feat: multi-Oracle server support with runtime switching

Complete implementation of multi-server Oracle database support:

Backend:
- Multi-pool Oracle with lazy loading per server
- Email-to-server cache for automatic server discovery
- JWT tokens include server_id claim
- /auth/check-identity and /auth/check-email endpoints
- /auth/my-servers endpoint for listing user's accessible servers
- Server switch with password re-authentication

Frontend:
- New ServerSelector component for header dropdown
- Multi-step login flow (identity → server → password)
- Server switching from header with password modal
- Mobile drawer menu with server selection
- Dark mode support for all new components
- URL bookmark support with ?server= query param

Scripts:
- Unified start.sh replacing start-prod.sh/start-test.sh
- Unified ssh-tunnel.sh with multi-server support
- Updated status.sh for new architecture

Tests:
- E2E tests for multi-server and single-server login flows
- Backend unit tests for all new endpoints
- Oracle multi-pool integration tests

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/modules/telegram/db/database.py

@@ -17,6 +17,9 @@ logger = logging.getLogger(__name__)
 DB_DIR = Path(__file__).parent.parent.parent / "data"
 DB_PATH = DB_DIR / "telegram_bot.db"
 
+# SQLite busy timeout in milliseconds (wait for locks instead of failing immediately)
+SQLITE_BUSY_TIMEOUT_MS = 5000
+
 
 async def get_db_connection() -> aiosqlite.Connection:
     """
@@ -41,6 +44,10 @@ async def init_database() -> None:
         logger.info(f"Database directory: {DB_DIR}")
 
         async with aiosqlite.connect(DB_PATH) as db:
+            # Enable WAL mode for better concurrent access
+            await db.execute("PRAGMA journal_mode=WAL")
+            # Set busy timeout to wait for locks instead of failing immediately
+            await db.execute(f"PRAGMA busy_timeout={SQLITE_BUSY_TIMEOUT_MS}")
             # Enable foreign keys
             await db.execute("PRAGMA foreign_keys = ON")