feat: add OCR service container (refs #64)

Add Python-based OCR service container (mvp-ocr) as the 6th service:
- Python 3.11-slim with FastAPI/uvicorn
- Tesseract OCR with English language pack
- pillow-heif for HEIC image support
- opencv-python-headless for image preprocessing
- Health endpoint at /health
- Unit tests for health, HEIC support, and Tesseract availability

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

ocr/app/main.py

@@ -0,0 +1,26 @@
+"""OCR Service FastAPI Application."""
+from fastapi import FastAPI
+
+from app.config import settings
+
+app = FastAPI(
+    title="MotoVaultPro OCR Service",
+    description="OCR processing service for vehicle documents",
+    version="1.0.0",
+)
+
+
+@app.get("/health")
+async def health_check() -> dict:
+    """Health check endpoint for container orchestration."""
+    return {"status": "healthy"}
+
+
+@app.get("/")
+async def root() -> dict:
+    """Root endpoint with service information."""
+    return {
+        "service": "mvp-ocr",
+        "version": "1.0.0",
+        "log_level": settings.log_level,
+    }