Feat/investing and debt page

[CjKhaled]

Adds dedicated Investments, Debts, and redesigned Savings pages to the frontend, fixes the signup flow to require email verification before login frontend-wise, and restores the missing PATCH /profile route for birthday updates during onboarding.

New Pages

• Investments — portfolio value stat cards, asset allocation donut chart, holdings table with per-holding gain/loss, retirement projections from the latest investing proposal, and recent investment transactions
• Debts — total debt and minimum payments stat cards, debt-free target date, debt breakdown donut, per-debt cards with APR/progress bars, payoff projections from the latest debt proposal, and recent debt payment transactions
• Savings (redesigned) — emergency fund tracking with real account balance (matched by account name), tiered progress bar toward 3-month and 6-month income targets, savings rate stat card, linked savings accounts list, and EF contribution history chart
• Check Email — post-registration interstitial showing "check your inbox" with a resend button
• Verify Email — handles the email verification link, calls the existing backend endpoint, shows success/error state

Signup Flow Fix

• Removed auto-login after registration in SignUpPage — the backend requires emailVerified: true before allowing login, so the old flow always failed
• Registration now redirects to /check-email with a resend option, and the email verification link lands on /verify-email which confirms the account before sending the user to login
• Currently in dev there is a UI bug because react strict mode fires useEffect twice. In prod this shouldn't be a problem.

Backend (TDD)

• GET /api/investments/holdings — returns the latest holdings snapshot (4 tests)
• GET /api/liabilities — returns the latest liability snapshot per account (4 tests)
• GET /api/transactions?category=X — adds server-side category filtering (4 tests)
• PATCH /api/auth/profile — restores the birthday update route lost during a prior merge (4 tests)
• Other
• Added DebtPaymentPlan and InvestmentPlan typed interfaces for proposal results
• Added Holding and Liability frontend type definitions
• Added financial goals display (badge chips) to the Budget page
• Added Investments and Debts nav items to the sidebar