feat: Add Trial Balance (Balanță de Verificare) feature

Comprehensive implementation of Trial Balance page with filtering,
pagination, and sorting capabilities.

Backend Changes:
- Added Pydantic models for Trial Balance (trial_balance.py)
  - TrialBalanceItem: Individual balance record
  - TrialBalanceFilters: Filter parameters
  - TrialBalancePagination: Pagination metadata
  - TrialBalanceResponse: Complete API response
- Created FastAPI router (/api/trial-balance) with:
  - Filtering by account number (cont) and description (denumire)
  - Pagination support (configurable page size)
  - Sorting on all columns (ascendent/descendent)
  - Company-based access control via JWT
  - Query against Oracle VBAL table
- Registered router in main.py

Frontend Changes:
- Created Pinia store (trialBalanceStore.js) with:
  - State management for trial balance data
  - Filters (luna, an, cont, denumire)
  - Pagination controls
  - Sorting functionality
  - Error handling and loading states
- Built TrialBalanceView.vue component featuring:
  - PrimeVue DataTable with responsive design
  - Period display (month/year)
  - Dual input filters (account number + description)
  - Debounced search (500ms)
  - Clear filters functionality
  - Formatted currency display (Romanian locale)
  - Balance columns (Debit/Credit) for:
    - Sold Precedent (Previous Balance)
    - Rulaj Lunar (Monthly Movement)
    - Sold Final (Final Balance)
  - Loading spinner and empty state
  - Mobile-friendly responsive layout
- Added route: /trial-balance with auth guard
- Added menu item in HamburgerMenu (Navigation section)
  - Icon: pi-calculator
  - Label: "Balanță de Verificare"

Technical Details:
- Follows established CSS architecture (no :deep(), uses design tokens)
- Consistent with InvoicesView patterns
- Implements proper error handling
- Uses Oracle NVL for null value handling
- ROW_NUMBER pagination for Oracle compatibility

Testing: Manual testing required (Phase 5)

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

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

reports-app/backend/app/main.py

@@ -25,7 +25,7 @@ from auth.middleware import AuthenticationMiddleware
 # from auth.routes import create_auth_router  # Fixed inline
 
 # Import routere locale
-from app.routers import invoices, dashboard, treasury, companies, telegram, cache
+from app.routers import invoices, dashboard, treasury, companies, telegram, cache, trial_balance
 
 # Auth endpoints pentru test
 from fastapi import APIRouter, HTTPException
@@ -317,6 +317,7 @@ app.include_router(dashboard.router, prefix="/api/dashboard", tags=["dashboard"]
 app.include_router(treasury.router, prefix="/api/treasury", tags=["treasury"])
 app.include_router(telegram.router, prefix="/api/telegram", tags=["telegram"])
 app.include_router(cache.router, prefix="/api", tags=["cache"])
+app.include_router(trial_balance.router, prefix="/api/trial-balance", tags=["trial-balance"])
 
 @app.get("/")
 async def root():