- Add S3 object verification after upload (size validation before DB commit)
- Add cleanup of S3 objects if DB commit fails
- Record upload duration_ms and user_agent
- Support X-Checksum-SHA256 header for client-side checksum verification
- Add already_existed flag to StorageResult for deduplication tracking
- Add status, error_message, client_checksum columns to Upload model
- Add UploadLock model for future 409 conflict detection
- Add consistency-check admin endpoint for detecting orphaned S3 objects
- Add migration 005_upload_enhancements.sql
- Backend: Python 3.12 with FastAPI, SQLAlchemy, boto3
- Frontend: React 18 with TypeScript, Vite build tooling
- Updated Dockerfile for multi-stage Node + Python build
- Updated CI pipeline for Python backend
- Removed old Go code (cmd/, internal/, go.mod, go.sum)
- Updated README with new tech stack documentation
