Adds a complete theming system with dark/light mode support and redesigns
the overview page with a modern card-based layout plus a 30-day staking
rewards bar chart.

NO CONSENSUS CHANGES - purely UI/client-side modifications.

Theme System:
- New ThemeManager class loads QSS stylesheets at runtime
- Dark theme (default) branded with Validity green (#43b581)
- Light theme preserves familiar classic look
- Theme preference persisted via QSettings across sessions
- Comprehensive dark.qss covering all Qt widget types (350+ lines)

Dashboard Redesign:
- Overview page restructured into 4 distinct cards:
  - Balance Card (top-left): available, pending, immature, stake, total
  - Staking Chart Card (top-right): 30-day bar chart + summary stats
  - Network Card (bottom-left): supply, staking %, weight, generation
  - Recent Transactions Card (bottom-right): last 5 transactions
- Cards use rounded corners and subtle borders for visual separation

Staking Rewards Chart:
- New StakingChartWidget (custom QPainter QWidget)
- Displays 30 daily bars showing staking rewards over time
- Validity green bars with rounded top corners
- Hover tooltips showing exact date and reward amount
- Y-axis with auto-scaled labels, X-axis with date labels
- Zero new backend work: reuses existing PrepareRangeForStakeReport() data

Code Quality Fixes:
- Renamed local round() to roundTo2() to avoid std::round conflict
- Fixed malformed iconset XML in overviewpage.ui
- Removed using namespace std at file scope
- Added Qt 5/6 compatibility for QDateTime::fromTime_t deprecation
- Removed hardcoded inline progress bar stylesheets (theme handles them)
- Fixed progress bar maximum value mismatches between .ui and .cpp

New files:
- src/qt/thememanager.h/.cpp
- src/qt/stakingchartwidget.h/.cpp
- src/qt/res/themes/dark.qss
- src/qt/res/themes/light.qss
- docs/plans/2026-02-25-dark-theme-dashboard-design.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Major visual overhaul to match validitytech.com aesthetic:
- Rewrite dark.qss with cosmic gradient palette, pill-shaped buttons,
  thin scrollbars, and modern typography
- Convert horizontal toolbar to vertical sidebar navigation
- Redesign splash screen with dark cosmic gradient and branded text
- Add theme picker (Dark/Light) to Options dialog Display tab
- Set QPalette alongside QSS for PlatformStyle compatibility
- Update all hardcoded colors across 10+ files for theme consistency
- Fix inline stylesheets in .ui forms (modal overlay, overview, send)
- Update guiconstants.h color constants for dark theme
- Enhance system tray tooltip with staking status details

Security fixes from full codebase audit:
- Fix CExtKey::Unserialize buffer overflow (missing length validation)
- Fix UnlockStaking case fall-through in passphrase dialog

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Backup Wizard:
- New guided multi-step backup dialog (QDialog + QStackedWidget)
- 4 pages: Intro, Choose Location, Progress, Complete
- Builds on existing walletModel->backupWallet() - zero backend changes
- Accessible via File > Backup Wizard menu item
- New files: backupwizard.h/.cpp

Network Peer Map:
- Custom QPainter world map widget showing connected peers
- Simplified continent outlines with peer dots color-coded by latency
- Green (<100ms), yellow (<300ms), red (>300ms) ping indicators
- Hover tooltips showing peer IP, version, ping, bytes in/out
- Lightweight IP geolocation using first-octet heuristic mapping
- Connection lines from center node to each peer
- Inbound peer indicator (white ring)
- Added as new "Peer Map" tab in Debug/RPC Console
- New files: peermapwidget.h/.cpp, geoip.h/.cpp

Build system updated: Makefile.qt.include, dark.qss styling

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Expanded tray icon menu with Overview, Transactions, Backup Wizard,
  and wallet lock/unlock quick actions
- Enhanced incoming transaction notifications to distinguish staking
  rewards with dedicated "Staking Reward!" title and reward-focused message
- Richer tray tooltip showing staking weight, network weight, and
  connection count alongside reward estimate
- Fixed branding: "Bitcoin network" -> "Validity network" in connection
  tooltip, default message title now uses PACKAGE_NAME
- Shortened staking status messages for cleaner display

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Added 526 lines to dark.qss covering send/receive forms, fee section,
  coin control stats, address book, transaction history, coin control
  dialog, options dialog, and global focus/disabled/tooltip states
- Fee section: radio button highlight, slider styling, label hierarchy
- Send page: icon button hover effects, validation states, add/clear
  button styling, monospace coin control stats
- Receive page: form label hierarchy, request table hover effects,
  show/remove button styling, QR dialog URI display
- Address book: new/copy/delete/export button styling with hover states
- Transaction view: filter bar inputs, table hover/select effects,
  context menu styling, date range widget
- Coin control: tree widget alternating rows, checkbox styling,
  select all button, item hover/select effects
- Global: disabled states, focus indicators, tooltip styling
- Fixed "Invalid Bitcoin address" -> "Invalid Validity address"
- Fixed Windows startup shortcut names Bitcoin -> Validity

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Three comprehensive reports based on JJ's request to explore
upgrading Validity to latest BlackCoin or Bitcoin Core:

1. Bitcoin Core 30.0 port feasibility (12-24 months, extreme risk)
2. BlackCoin More 26.x rebase feasibility (RECOMMENDED, 1-3 months)
3. PoS consensus code inventory (~1,670 lines across 12 files)

Key finding: BlackCoin More 26.x is the clear best path — same PoS
kernel, JJ already contributes to it, proven upgrade path exists.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Replaced all remaining user-facing "Bitcoin" references with "Validity":
- Address book: "Bitcoin addresses" -> "Validity addresses" (send/receive)
- Send page: "Send coins to a Bitcoin address" -> Validity
- Sign/Verify: "Bitcoin addresses" -> "Validity addresses"
- Edit address: "not a valid Bitcoin address" -> Validity
- Address input placeholder: "Enter a Bitcoin address" -> Validity
- Payment server: IPC name "BitcoinQt" -> "ValidityQt"
- Payment server: "Bitcoin address" error -> Validity
- Fatal error: "Bitcoin can no longer continue" -> Validity
- Help action: removed redundant "Bitcoin" from command-line options text

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Updated all user-facing tooltip and description text in .ui files:
- optionsdialog: UPnP tooltip, SOCKS5 proxy descriptions (3 strings)
- overviewpage: sync warning tooltips (2 strings)
- intro: data directory description
- receivecoinsdialog: payment request message notes (2 strings)
- sendcoinsentry: address tooltip, URI reference, network note (3 strings)
- signverifymessagedialog: all sign/verify address references (4 strings)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Complete rewrite of light.qss from 51 to 700+ lines matching dark theme
  coverage across all pages (cards, sidebar, tabs, tables, dialogs, etc.)
- New CardDragDropManager (carddragdrop.h/.cpp) for dashboard card reordering
  via event filter, with drop indicator and QSettings persistence
- Integrate drag-drop into OverviewPage for transactionsCard and networkCard
- Update HANDOFF.md to reflect all-phases-complete status

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- All 4 dashboard cards now draggable (balance, staking, transactions, network)
  via flattened VBoxLayout instead of nested HBoxLayout
- Cards are resizable by dragging bottom edge (persisted to QSettings)
- Fix dark theme sidebar icons: recolorToolbarIcons() colorizes toolbar
  button icons using QPalette::WindowText, auto-updates on theme change
- Include pre-built validity-qt.exe binary

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Replace flat 4-card vertical stack with QSplitter grid:
  top row (balance | staking chart side-by-side), transactions, network
- All splitter sections resizable with native drag handles
- Splitter sizes persisted to QSettings across restarts
- Fix ALL action icons (menus + toolbar) by colorizing with
  QPalette::WindowText - auto-updates on theme change
- Add QSplitter handle styling to both dark and light themes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Remove ~15 duplicate/redundant QSS selectors in dark.qss and light.qss
  that caused double widget-tree walks during style resolution
- Simplify ancestor-prefixed selectors (QDialog#X QLabel#Y → QLabel#Y)
  where the ID alone is unique, avoiding unnecessary tree traversal
- Add QPixmap paint cache to StakingChartWidget — only rebuilds when
  data, widget size, or hover state changes; paintEvent just blits cache
- Enable uniform item sizes on transaction list for faster scrolling
- Merge conflicting CoinControlDialog QTreeWidget blocks into single
  class-based selector with combined properties

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The staking stats, supply, and network weight computations scan the
entire wallet transaction map and UTXO set while holding cs_main,
blocking the UI for seconds on fully synced wallets. This change:

- Defers the first heavy computation by 2 seconds via QTimer so the
  dashboard cards, chart, and transaction list render immediately
- Caches wallet tx count — skips GetsStakeSubTotal rescan if no new
  transactions have arrived since the last computation
- Caches UTXO supply by block height — avoids redundant GetSupply()
  calls when the chain tip hasn't changed

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Replace fixed QSplitter layout with DashboardGridManager — a full
drag-and-drop system supporting 2-column card arrangements:

- Cards can be dragged between left/right columns and reordered
  within a column (grab any non-interactive area to drag)
- Floating thumbnail preview follows the cursor during drag
- Green indicator bar shows the exact drop position
- Both column widths and card heights are resizable via splitter handles
- Layout is persisted to QSettings (card positions + splitter sizes)
- Default layout: balance, staking, network on left; transactions on right
- Escape key cancels an in-progress drag
- Interactive widgets (buttons, inputs, scroll areas) are excluded
  from drag initiation so normal card interactions still work

Also adds checkpoint validation to the stats caching:
- Network weight cache invalidates if drift exceeds 20%
- Staking report recalculates when staking status changes
- Copyright headers updated to include all contributors

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Security fixes from comprehensive triple-agent audit:
- CRITICAL: Remove #include "rpc/blockchain.cpp" (ODR violation,
  namespace pollution); use proper extern declarations and headers
- CRITICAL: Add cs_wallet lock for mapWallet.size(), IsStaking(),
  and GetStakeWeight() calls from UI thread (data race)
- CRITICAL: Initialize lastStaking bool (was undefined behavior)
- CRITICAL: Add bounds check for aRange[30-34] staking report access
- Fix integer overflow in daily reward calculation (saturation guard)
- Remove roundTo2() from CAmount contexts (was no-op, confusing)
- Remove using namespace boost (namespace pollution)

Performance fix:
- Defer recolorToolbarIcons() to after window is visible via
  QTimer::singleShot(0) — was blocking splash-to-dashboard
- Cache original icons to prevent degradation on theme switches

Additional security hardening:
- Passphrase: use QByteArray with immediate zeroing instead of
  leaking through std::string temporary on ordinary heap
- DashboardGridManager: use delete (not deleteLater) in destructor
  to prevent memory leak on application shutdown
- QTimer::singleShot: use QPointer guard for deferred stats load

Peer map bug fix:
- GeoIP: handle IPv4-mapped IPv6 addresses ([::ffff:x.x.x.x]:port)
  instead of returning (0,0) which overlaps center node
- Pure IPv6 peers now spread visually using address hash
- Force initial updatePeerMap() call in setClientModel()

Splash screen:
- Show full copyright chain (Bitcoin Core, Blackcoin, Blackcoin More,
  Radium Core, Validity) matching the loading screen

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Only create OverviewPage and SendCoinsDialog at startup. Defer
TransactionView (heaviest — loads full tx table model),
ReceiveCoinsDialog, and AddressBookPage until first navigation.
Eliminates ~60% of widget construction from the startup path.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Replace broken lazy page construction (caused "Not Responding" freeze)
with deferred model loading: all widgets created eagerly but the heavy
transactionView->setModel() is deferred via QTimer::singleShot(0)
so the dashboard renders in the first event loop pass.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The real bottleneck was getTransactionTableModel() being called in
OverviewPage::setWalletModel() and WalletView::setWalletModel(),
triggering refreshWallet() which iterates ALL wallet transactions
with crypto ops (IsMine, ExtractDestination) under LOCK2.

Fix: defer transaction filter setup (500ms) and transaction view
model + signal connection (750ms) so dashboard renders with balances
first, transactions populate after.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Root cause: refreshWallet() iterates ALL 36,104 wallet transactions
calling decomposeTransaction() (crypto ops) on each, blocking the
UI thread for 10-30+ seconds. No amount of deferring helps — the
work itself must move off the UI thread.

Fix: TransactionTableModel now spawns a std::thread to load
wallet transactions in the background. The UI renders immediately
with an empty transaction list, and when the background load
completes, onBackgroundRefreshComplete() swaps in the data via
beginResetModel()/endResetModel(). Incremental updates and
confirmation updates are skipped during background loading.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The background thread was holding LOCK2(cs_main, cs_wallet) for the
entire 36K transaction scan, starving the UI thread. Also, TRY_LOCK
was scoped incorrectly (released before blocking LOCK re-acquired).

Fix: background thread processes in 200-tx batches with 10ms yields.
UI functions use TRY_LOCK at function scope (recursive_mutex allows
nested LOCK calls) and reschedule on contention instead of blocking.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>