feat: production readiness improvements
## Error Handling
- Add GlobalErrorBoundary with error classification and recovery
- Add custom error types (SecurityError, ConnectionError, TimeoutError)
- Fix ErrorAlert component syntax errors
## Offline Mode
- Add offlineStore for offline state management
- Implement message queue with localStorage persistence
- Add exponential backoff reconnection (1s→60s)
- Add OfflineIndicator component with status display
- Queue messages when offline, auto-retry on reconnect
## Security Hardening
- Add AES-256-GCM encryption for chat history storage
- Add secure API key storage with OS keychain integration
- Add security audit logging system
- Add XSS prevention and input validation utilities
- Add rate limiting and token generation helpers
## CI/CD (Gitea Actions)
- Add .gitea/workflows/ci.yml for continuous integration
- Add .gitea/workflows/release.yml for release automation
- Support Windows Tauri build and release
## UI Components
- Add LoadingSpinner, LoadingOverlay, LoadingDots components
- Add MessageSkeleton, ConversationListSkeleton skeletons
- Add EmptyMessages, EmptyConversations empty states
- Integrate loading states in ChatArea and ConversationList
## E2E Tests
- Fix WebSocket mock for streaming response tests
- Fix approval endpoint route matching
- Add store state exposure for testing
- All 19 core-features tests now passing
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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