feat: Add multiple TVA entries support for Romanian receipts

- Add TvaEntry schema supporting multiple TVA rates (A, B, C, D codes)
- Update OCR extractor to extract multiple TVA entries from receipts
- Support both old (19%, 9%, 5%) and new Romanian rates (21%, 11% from Aug 2025)
- Add tva_breakdown, tva_total, items_count, vendor_address to Receipt model
- Update OCRPreview.vue to display TVA entries with rate badges
- Add "Detalii Suplimentare" section in ReceiptCreateView with editable TVA table
- Add TVA breakdown display in ReceiptDetailView
- Create database migration for new TVA columns

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

data-entry-app/backend/app/db/models/receipt.py

@@ -51,6 +51,12 @@ class Receipt(SQLModel, table=True):
     amount: Decimal = Field(decimal_places=2, max_digits=15)
     description: Optional[str] = Field(default=None, max_length=500)
 
+    # TVA info (extracted from OCR) - stored as JSON for multiple entries
+    tva_breakdown: Optional[str] = Field(default=None, max_length=1000)  # JSON: [{"code":"A","percent":19,"amount":"15.20"}]
+    tva_total: Optional[Decimal] = Field(default=None, decimal_places=2, max_digits=15)
+    items_count: Optional[int] = Field(default=None)
+    vendor_address: Optional[str] = Field(default=None, max_length=500)
+
     # Expense type (for auto-generating accounting entries)
     expense_type_code: Optional[str] = Field(default=None, max_length=20)