feat(cli): add private NanoShare sync client

- Add a separate installable NanoShare CLI package under cli/.
- Implement browser login with local callback and refresh-token config.
- Add upload, list, download, sync, and watch CLI commands.
- Add private owner-only file download endpoint for CLI downloads.
- Add CLI auth endpoints for browser login and token refresh.
- Return file_id from ServiceLink uploads for reliable sync state.
- Exclude the CLI package from NanoShare container builds.
- Include tests for private downloads and sync state updates.

.dockerignore

@@ -0,0 +1,15 @@
+.git
+.venv
+__pycache__
+.pytest_cache
+.ruff_cache
+*.pyc
+*.pyo
+*.pyd
+.env
+testing/.env
+access.log
+valkey_data
+redisinsight
+uploads
+cli