feat: add core OCR API integration (refs #65)

OCR Service (Python/FastAPI):
- POST /extract for synchronous OCR extraction
- POST /jobs and GET /jobs/{job_id} for async processing
- Image preprocessing (deskew, denoise) for accuracy
- HEIC conversion via pillow-heif
- Redis job queue for async processing

Backend (Fastify):
- POST /api/ocr/extract - authenticated proxy to OCR
- POST /api/ocr/jobs - async job submission
- GET /api/ocr/jobs/:jobId - job polling
- Multipart file upload handling
- JWT authentication required

File size limits: 10MB sync, 200MB async
Processing time target: <3 seconds for typical photos

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

backend/src/features/CLAUDE.md

@@ -14,6 +14,7 @@ Feature capsule directory. Each feature is 100% self-contained with api/, domain
 | `fuel-logs/` | Fuel consumption tracking | Fuel log CRUD, statistics |
 | `maintenance/` | Maintenance record management | Service records, reminders |
 | `notifications/` | Email and push notifications | Alert system, email templates |
+| `ocr/` | OCR proxy to mvp-ocr service | Image text extraction, async jobs |
 | `onboarding/` | User onboarding flow | First-time user setup |
 | `platform/` | Vehicle data and VIN decoding | Make/model lookup, VIN validation |
 | `stations/` | Gas station search and favorites | Google Maps integration, station data |