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>

docker-compose.yml

@@ -164,6 +164,24 @@ services:
       - "traefik.http.services.mvp-backend.loadbalancer.healthcheck.timeout=10s"
       - "traefik.http.services.mvp-backend.loadbalancer.passhostheader=true"
 
+  # Application Services - OCR Processing
+  mvp-ocr:
+    build:
+      context: ./ocr
+      dockerfile: Dockerfile
+    container_name: mvp-ocr
+    restart: unless-stopped
+    environment:
+      LOG_LEVEL: info
+    networks:
+      - backend
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://localhost:8000/health"]
+      interval: 30s
+      timeout: 10s
+      retries: 3
+      start_period: 30s
+
   # Database Services - Application PostgreSQL
   mvp-postgres:
     image: ${REGISTRY_MIRRORS:-git.motovaultpro.com/egullickson/mirrors}/postgres:18-alpine