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/models/calendar.py

@@ -0,0 +1,19 @@
+"""
+Calendar period models for accounting period selector
+"""
+from pydantic import BaseModel
+from typing import List, Optional
+
+
+class CalendarPeriod(BaseModel):
+    """Model for an accounting period"""
+    an: int           # Year
+    luna: int         # Month (1-12)
+    display_name: str # Format: "Decembrie 2025"
+
+
+class CalendarPeriodsResponse(BaseModel):
+    """Response model for calendar periods list"""
+    periods: List[CalendarPeriod]
+    current_period: Optional[CalendarPeriod] = None  # Most recent period
+    total_count: int

reports-app/backend/app/models/invoice.py

@@ -44,8 +44,8 @@ class InvoiceFilter(BaseModel):
     """Filtru pentru căutarea facturilor"""
     company: str = Field(description="Codul firmei (schema Oracle)")
     partner_type: Literal["CLIENTI", "FURNIZORI"] = Field(description="Tipul partenerului")
-    date_from: Optional[date] = Field(description="Data de început")
-    date_to: Optional[date] = Field(description="Data de sfârșit")
+    luna: Optional[int] = Field(default=None, ge=1, le=12, description="Luna contabilă (1-12)")
+    an: Optional[int] = Field(default=None, ge=2000, le=2100, description="Anul contabil")
     partner_name: Optional[str] = Field(description="Filtru după nume")
     cont: Optional[str] = Field(description="Filtru după cont contabil")
     only_unpaid: bool = Field(default=True, description="Doar neachitate")

reports-app/backend/app/models/treasury.py

@@ -25,6 +25,8 @@ class RegisterFilter(BaseModel):
     """Filtre pentru registrul de casă și bancă"""
     company: str
     register_type: Optional[str] = None  # BANCA_LEI, BANCA_VALUTA, CASA_LEI, CASA_VALUTA sau None pentru toate
+    luna: Optional[int] = None  # Luna contabilă (1-12) pentru PACK_SESIUNE
+    an: Optional[int] = None  # Anul contabil pentru PACK_SESIUNE
     date_from: Optional[datetime] = None
     date_to: Optional[datetime] = None
     partner_name: Optional[str] = None