feat: Add accounting period selector for all views

- Add PeriodSelectorMini component for global period selection
- Add accountingPeriod store for shared period state
- Add calendar service/router/model for available periods API
- Update Dashboard, Invoices, Trial Balance, Bank/Cash Register views
  to respect selected period
- Fix Trial Balance navigation sync bug (period now syncs on mount)
- Update backend services to accept luna/an parameters

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

reports-app/backend/app/services/calendar_service.py

@@ -0,0 +1,78 @@
+"""
+Calendar service for fetching available accounting periods
+"""
+import sys
+import os
+sys.path.append(os.path.join(os.path.dirname(__file__), '../../../../shared'))
+
+from database.oracle_pool import oracle_pool
+from ..models.calendar import CalendarPeriod, CalendarPeriodsResponse
+from ..cache.decorators import cached
+import logging
+
+logger = logging.getLogger(__name__)
+
+
+class CalendarService:
+    """Service for calendar/accounting period operations"""
+
+    # Romanian month names for display
+    MONTH_NAMES_RO = [
+        "Ianuarie", "Februarie", "Martie", "Aprilie", "Mai", "Iunie",
+        "Iulie", "August", "Septembrie", "Octombrie", "Noiembrie", "Decembrie"
+    ]
+
+    @staticmethod
+    @cached(cache_type='schema', key_params=['company_id'])
+    async def _get_schema(company_id: int) -> str:
+        """Get schema for company (CACHED 24h)"""
+        async with oracle_pool.get_connection() as connection:
+            with connection.cursor() as cursor:
+                cursor.execute("""
+                    SELECT schema FROM CONTAFIN_ORACLE.v_nom_firme
+                    WHERE id_firma = :company_id
+                """, {'company_id': company_id})
+                result = cursor.fetchone()
+                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:
+        """
+        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)
+        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:
+            with connection.cursor() as cursor:
+                cursor.execute(f"""
+                    SELECT anul, luna
+                    FROM {schema}.calendar
+                    ORDER BY anul DESC, luna DESC
+                """)
+                rows = cursor.fetchall()
+
+                periods = []
+                for row in rows:
+                    an, luna = row[0], row[1]
+                    month_name = CalendarService.MONTH_NAMES_RO[luna - 1]
+                    periods.append(CalendarPeriod(
+                        an=an,
+                        luna=luna,
+                        display_name=f"{month_name} {an}"
+                    ))
+
+                current_period = periods[0] if periods else None
+
+                logger.info(f"Loaded {len(periods)} accounting periods for company {company_id}")
+
+                return CalendarPeriodsResponse(
+                    periods=periods,
+                    current_period=current_period,
+                    total_count=len(periods)
+                )