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/QUICK-ENV-REFERENCE.md

@@ -21,17 +21,17 @@ vim backend/.env.prod
 #    - SMTP_PASSWORD
 
 # 4. Start production
-./start-prod.sh
+./start.sh prod
 ```
 
 ## 📋 Daily Usage
 
 ```bash
 # Production (uses .env.prod automatically)
-./start-prod.sh
+./start.sh prod
 
 # Test Environment (uses .env.test automatically)
-./start-test.sh
+./start.sh test
 
 # Quick Restart (uses existing .env)
 ./start-backend.sh restart
@@ -45,7 +45,7 @@ vim backend/.env.prod    # Production
 vim backend/.env.test   # Test
 
 # 2. Restart to apply changes
-./start-prod.sh
+./start.sh prod
 ```
 
 ## 📁 Which File to Edit?