feat: SecretStorage migration and UI state persistence

[rhoades-brown]

Summary

Implements API enhancements available in Obsidian 1.12.7 (current public version). This is a security and UX improvement release.

Changes

SecretStorage migration (1.11.4)

• Main PAT: Migrated from plaintext data.json to app.secretStorage.setSecret('github-pat', token). Token is no longer persisted in data.json.
• Additional repo tokens: Each repo's token stored as github-pat-{repoId} in SecretStorage.
• Auto-migration: On first load after upgrade, existing plaintext tokens are automatically migrated to SecretStorage and cleared from data.json.
• Runtime unchanged: settings.auth.token still works in memory; only persistence layer changed.

loadLocalStorage for UI state (1.8.7)

• SyncView panel collapse state (commits expanded, logs expanded) persisted per-vault via app.loadLocalStorage/app.saveLocalStorage.
• Panel state survives view close/reopen and Obsidian restart.

Version bump

• minAppVersion bumped from 1.7.2 to 1.12.7
• versions.json updated with 0.5.0 mapping

Commits

1. feat: migrate main PAT to SecretStorage for encrypted storage
2. feat: migrate additional repo tokens to SecretStorage
3. feat: persist SyncView panel state with loadLocalStorage
4. chore: bump minAppVersion to 1.12.7

Checklist

• Build passes
• Lint clean (0 errors/warnings)
• All 119 tests pass
• Mocks updated with SecretStorage, loadLocalStorage/saveLocalStorage