fix: Add bank/cash name sorting to treasury register

- Add bancasa as third sorting criterion (date, number, bank name)
- Sort null-date rows (previous balances) alphabetically by bank name
- Sort bank names alphabetically in PDF export
- Improve window function for cumulative balance calculation

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

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

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

@@ -3,25 +3,32 @@ from decimal import Decimal
 from datetime import datetime
 from typing import Optional, List
 
+class AccountingPeriod(BaseModel):
+    """Model pentru perioada contabilă"""
+    an: Optional[int] = None
+    luna: Optional[int] = None
+
 class BankCashRegister(BaseModel):
     """Model pentru Registrul de Casă și Bancă"""
     nume: str
-    nract: int
-    dataact: datetime
+    nract: Optional[int] = None
+    dataact: Optional[datetime] = None
     nume_cont_bancar: str    # din vbalanta_parteneri.nume
     incasari: Decimal
     plati: Decimal
     sold: Decimal
-    valuta: str
+    valuta: Optional[str] = None
     tip_registru: str  # "BANCA LEI", "CASA VALUTA" etc
     explicatia: str
 
 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
     date_from: Optional[datetime] = None
     date_to: Optional[datetime] = None
     partner_name: Optional[str] = None
+    bank_account: Optional[str] = None  # Filter for specific bank/cash account (bancasa)
     page: int = 1
     page_size: int = 50
 
@@ -34,4 +41,5 @@ class RegisterListResponse(BaseModel):
     total_plati: Decimal
     page: int
     page_size: int
-    has_more: bool
+    has_more: bool
+    accounting_period: Optional[AccountingPeriod] = None