feat: Enhance invoice management with PDF optimization and date fixes

Optimize PDF export layout with compact columns and more space for partner names.
Add accounting period display to invoices matching Trial Balance format. Fix date
filtering to use local timezone instead of UTC. Update invoice ordering to
chronological sequence (DATAACT, NRACT, NUME).

**Backend changes:**
- Add accounting period query from calendar table
- Add currency (valuta) and cont filter support
- Change invoice ordering to chronological (DATAACT ASC, NRACT ASC, NUME)
- Add accounting_period field to InvoiceListResponse model

**Frontend changes:**
- Optimize PDF column widths (37% for partner names, compact numeric columns)
- Add custom column width support in exportUtils
- Fix date conversion from UTC to local timezone (prevents day shift)
- Add accounting period display in PDF exports
- Enhance E2E test coverage

**Cleanup:**
- Remove obsolete Trial Balance feature documentation

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

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

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

@@ -19,7 +19,7 @@ async def get_bank_cash_register(
     date_to: Optional[str] = Query(None, description="Data sfârșit (YYYY-MM-DD)"),
     partner_name: Optional[str] = Query(None, description="Filtru nume partener"),
     page: int = Query(1, ge=1, description="Pagina"),
-    page_size: int = Query(50, ge=1, le=1000, description="Mărimea paginii"),
+    page_size: int = Query(50, ge=1, le=10000000, description="Mărimea paginii"),
     current_user: CurrentUser = Depends(get_current_user)
 ):
     """