docs: add Solana roadmap

[WRRicht3r]

Summary

Describe the change and why it’s needed.

Related Issue

Closes # (or) Relates to #

Type of Change

• feat (new feature)
• fix (bug fix)
• refactor (no functional change)
• chore/build (tooling, CI, deps)
• docs (README/AGENTS, comments)

Screenshots / Videos

If UI changes, include before/after.

Test Plan

Commands run locally:

./gradlew detektAll
./gradlew runTest
./gradlew :app:lint

Additional checks and scenarios covered:

Risks & Rollout

Potential impact, migrations, or config/secrets required.

Checklist

• Linked an issue and added a clear description
• Added/updated tests for changed code (where applicable)
• Updated docs (README/AGENTS) when behavior or commands changed
• Ran detektAll, runTest, and :app:lint locally (or via CI)
• No secrets or local.properties committed

[WRRicht3r]

Solana account scaffolding is now wired through every layer:

• Added Solana constants, a slip‑0010 ed25519 derivation helper, and a
  secret store/test harness (common/src/main/java/jp/co/soramitsu/common/
  domain/SolanaConstants.kt:1, common/src/main/java/jp/co/soramitsu/common/
  utils/solana/SolanaKeyFactory.kt:1, common/src/main/java/jp/co/soramitsu/
  common/data/secrets/v3/SolanaSecretStore.kt:1, common/src/test/java/jp/co/
  soramitsu/common/utils/solana/SolanaKeyFactoryTest.kt:5). The DI module now
  exposes the new store and we pull in the solanaj dependency so ed25519 keys
  can be derived consistently (common/build.gradle:58, common/src/main/java/
  jp/co/soramitsu/common/di/modules/CommonModule.kt:235).
• MetaAccountLocal/Room gained a solanaPublicKey column (migration 74→75)
  and every mapper/model/import path now carries it, so Solana data
  survives migrations and feeds the UI (core-db/src/main/java/jp/co/
  soramitsu/coredb/model/MetaAccountLocal.kt:16, core-db/src/main/java/jp/
  co/soramitsu/coredb/migrations/Migrations.kt:8, feature-account-api/src/
  main/java/jp/co/soramitsu/account/api/domain/model/MetaAccount.kt:25).
  Account creation/import/export/backup flows derive Solana keypairs
  alongside Substrate/EVM, store them via the new secret store, expose
  them for backup/Google sync, and teach the wallet UI when to show Solana-
  specific options (feature-account-impl/src/main/java/jp/co/soramitsu/
  account/impl/data/repository/AccountRepositoryDelegate.kt:96, feature-
  account-impl/src/main/java/jp/co/soramitsu/account/impl/data/repository/
  AccountRepositoryImpl.kt:92, feature-account-impl/src/main/java/jp/co/
  soramitsu/account/impl/domain/AccountInteractorImpl.kt:368, feature-wallet-
  impl/src/main/java/jp/co/soramitsu/wallet/impl/presentation/balance/list/
  BalanceListViewModel.kt:645).
• Compose/strings now include Solana labels so connected-account dialogs
  and warnings mention the new ecosystem (common/src/main/res/values/
  strings.xml:358, feature-account-impl/src/main/java/jp/co/soramitsu/account/
  impl/presentation/account/details/AccountDetailsViewModel.kt:121), and the
  mnemonic/backup/create flows include Solana in their payloads (feature-
  account-impl/src/main/java/jp/co/soramitsu/account/impl/presentation/
  account/create/CreateAccountViewModel.kt:74, feature-account-impl/src/
  main/java/jp/co/soramitsu/account/impl/presentation/mnemonic/confirm/
  ConfirmMnemonicPayload.kt:12).

[WRRicht3r]

Implemented full Solana plumbing end-to-end.

• Added shared Solana constants plus a Kotlin slip‑0010 ed25519 derivation
  utility and deterministic test so we can derive SPL keys straight from
  the wallet mnemonic (common/src/main/java/jp/co/soramitsu/common/domain/
  SolanaConstants.kt:1, common/src/main/java/jp/co/soramitsu/common/utils/
  solana/SolanaKeyFactory.kt:1, common/src/test/java/jp/co/soramitsu/
  common/utils/solana/SolanaKeyFactoryTest.kt:5). Introduced a dedicated
  SolanaSecretStore and wired the module’s DI to expose it (common/src/main/
  java/jp/co/soramitsu/common/data/secrets/v3/SolanaSecretStore.kt:1, common/
  src/main/java/jp/co/soramitsu/common/di/modules/CommonModule.kt:25), plus
  surfaced new UI string resources.
• Extended storage/domain layers to remember Solana keys: MetaAccountLocal now
  persists solanaPublicKey with a 74→75 migration, and the MetaAccount model/
  has‑flags handle 🐸 assets and addresses consistently (core-db/src/main/
  java/jp/co/soramitsu/coredb/model/MetaAccountLocal.kt:16, core-db/src/main/
  java/jp/co/soramitsu/coredb/migrations/Migrations.kt:1, feature-account-api/
  src/main/java/jp/co/soramitsu/account/api/domain/model/MetaAccount.kt:25).
  The repository derives/stores Solana secrets when a Substrate/EVM wallet is
  created, exposes them for backup/export, and the key-provider can now hand
  a Solana keypair to signing code (feature-account-impl/src/main/java/jp/
  co/soramitsu/account/impl/data/repository/AccountRepositoryDelegate.kt:96,
  feature-account-impl/src/main/java/jp/co/soramitsu/account/impl/data/
  repository/AccountRepositoryImpl.kt:92, feature-account-impl/src/main/java/
  jp/co/soramitsu/account/impl/data/repository/KeyPairRepository.kt:11).
• Updated UI/backups/workflows so Solana behaves like the other ecosystems:
  creation flows now include Solana in the mnemonic payload, backup
  screens/gateway logic show the correct title, wallet state uses the
  new chain set when deciding whether to show the “join Substrate/
  EVM” banner, and the ecosystem options dialog understands Solana chain
  IDs (feature-account-impl/src/main/java/jp/co/soramitsu/account/impl/
  presentation/account/create/CreateAccountViewModel.kt:66, feature-
  account-impl/src/main/java/jp/co/soramitsu/account/impl/presentation/
  mnemonic/confirm/ConfirmMnemonicViewModel.kt:130, feature-account-
  impl/src/main/java/jp/co/soramitsu/account/impl/presentation/account/
  details/AccountDetailsViewModel.kt:121, feature-wallet-impl/src/
  main/java/jp/co/soramitsu/wallet/impl/presentation/balance/list/
  BalanceListViewModel.kt:645).