refactor: final cleanup — delete legacy auth, clean deps, fix hash, migrate to uv
- Delete root auth/ directory (legacy Flask providers, orphaned)
- Clean requirements.txt: remove Flask, gunicorn, authlib, sendgrid,
anthropic, openai, argon2-cffi (9 unused deps)
- Fix hash computation in orchestrator: MD5 of parquet mtime+size
(CLI sync now skips unchanged tables correctly)
- Migrate pip → uv in CLAUDE.md, scripts/init.sh, pyproject.toml
- Sync pyproject.toml dependencies with requirements.txt
578 tests passing.