feat: Add OCR integration for automatic receipt data extraction

Implement Tesseract-based OCR to automatically extract vendor name,
date, total amount, and VAT from uploaded receipt images/PDFs,
reducing manual data entry and improving accuracy.

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

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

data-entry-app/backend/app/main.py

@@ -71,9 +71,10 @@ async def health_check():
 
 
 # Import and include routers
-from app.routers import receipts
+from app.routers import receipts, ocr
 
 app.include_router(receipts.router, prefix="/api/receipts", tags=["receipts"])
+app.include_router(ocr.router, prefix="/api/ocr", tags=["ocr"])
 
 
 # Root endpoint