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/models/trial_balance.py

@@ -0,0 +1,84 @@
+"""
+Pydantic models for Trial Balance (Balanță de Verificare)
+Maps to Oracle VBAL table
+"""
+from pydantic import BaseModel, Field
+from typing import Optional, List
+from decimal import Decimal
+
+class TrialBalanceItem(BaseModel):
+    """
+    Individual trial balance record from VBAL table
+    """
+    cont: str = Field(description="Număr cont contabil")
+    dcont: str = Field(description="Denumire cont")
+    sold_precedent_debit: Decimal = Field(description="Sold precedent debit", decimal_places=2)
+    sold_precedent_credit: Decimal = Field(description="Sold precedent credit", decimal_places=2)
+    rulaj_lunar_debit: Decimal = Field(description="Rulaj lunar debit", decimal_places=2)
+    rulaj_lunar_credit: Decimal = Field(description="Rulaj lunar credit", decimal_places=2)
+    sold_final_debit: Decimal = Field(description="Sold final debit", decimal_places=2)
+    sold_final_credit: Decimal = Field(description="Sold final credit", decimal_places=2)
+
+    class Config:
+        from_attributes = True
+
+
+class TrialBalanceFilters(BaseModel):
+    """
+    Filters applied to trial balance data
+    """
+    luna: int = Field(description="Luna (1-12)")
+    an: int = Field(description="An")
+    cont_filter: Optional[str] = Field(default=None, description="Filtru număr cont (partial match)")
+    denumire_filter: Optional[str] = Field(default=None, description="Filtru denumire cont (partial match, case-insensitive)")
+
+
+class TrialBalancePagination(BaseModel):
+    """
+    Pagination metadata
+    """
+    total_items: int = Field(description="Total number of items")
+    total_pages: int = Field(description="Total number of pages")
+    current_page: int = Field(description="Current page number")
+    page_size: int = Field(description="Items per page")
+
+
+class TrialBalanceResponse(BaseModel):
+    """
+    Complete response for trial balance endpoint
+    """
+    success: bool = Field(default=True, description="Request success status")
+    data: dict = Field(description="Trial balance data with items, pagination, and filters")
+
+    class Config:
+        schema_extra = {
+            "example": {
+                "success": True,
+                "data": {
+                    "items": [
+                        {
+                            "cont": "4111",
+                            "dcont": "Furnizori interni",
+                            "sold_precedent_debit": 0.00,
+                            "sold_precedent_credit": 15000.00,
+                            "rulaj_lunar_debit": 5000.00,
+                            "rulaj_lunar_credit": 8000.00,
+                            "sold_final_debit": 0.00,
+                            "sold_final_credit": 18000.00
+                        }
+                    ],
+                    "pagination": {
+                        "total_items": 150,
+                        "total_pages": 3,
+                        "current_page": 1,
+                        "page_size": 50
+                    },
+                    "filters_applied": {
+                        "luna": 11,
+                        "an": 2025,
+                        "cont_filter": None,
+                        "denumire_filter": "furnizori"
+                    }
+                }
+            }
+        }