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/reports/services/calendar_service.py

@@ -3,6 +3,7 @@ Calendar service for fetching available accounting periods
 """
 # import sys  # Removed - no longer needed
 import os
+from typing import Optional
 
 from shared.database.oracle_pool import oracle_pool
 from ..models.calendar import CalendarPeriod, CalendarPeriodsResponse
@@ -22,10 +23,10 @@ class CalendarService:
     ]
 
     @staticmethod
-    @cached(cache_type='schema', key_params=['company_id'])
-    async def _get_schema(company_id: int) -> str:
+    @cached(cache_type='schema', key_params=['company_id', 'server_id'])
+    async def _get_schema(company_id: int, server_id: Optional[str] = None) -> str:
         """Get schema for company (CACHED 24h)"""
-        async with oracle_pool.get_connection() as connection:
+        async with oracle_pool.get_connection(server_id) as connection:
             with connection.cursor() as cursor:
                 cursor.execute("""
                     SELECT schema FROM CONTAFIN_ORACLE.v_nom_firme
@@ -35,19 +36,19 @@ class CalendarService:
                 return result[0] if result else None
 
     @staticmethod
-    @cached(cache_type='calendar_periods', key_params=['company_id'])
-    async def get_available_periods(company_id: int) -> CalendarPeriodsResponse:
+    @cached(cache_type='calendar_periods', key_params=['company_id', 'server_id'])
+    async def get_available_periods(company_id: int, server_id: Optional[str] = None) -> CalendarPeriodsResponse:
         """
         Get all available accounting periods for a company (CACHED 1h)
 
         Returns periods ordered by year DESC, month DESC with Romanian month names.
         """
-        schema = await CalendarService._get_schema(company_id)
+        schema = await CalendarService._get_schema(company_id, server_id)
         if not schema:
             logger.warning(f"Schema not found for company {company_id}")
             return CalendarPeriodsResponse(periods=[], current_period=None, total_count=0)
 
-        async with oracle_pool.get_connection() as connection:
+        async with oracle_pool.get_connection(server_id) as connection:
             with connection.cursor() as cursor:
                 cursor.execute(f"""
                     SELECT anul, luna