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.

cli/pyproject.toml

@@ -0,0 +1,16 @@
+[project]
+name = "nanoshare-cli"
+version = "0.1.0"
+description = "NanoShare desktop CLI and folder sync client"
+readme = "README.md"
+requires-python = ">=3.11"
+dependencies = [
+  "httpx==0.28.1",
+]
+
+[project.scripts]
+nanoshare = "nanoshare_client.cli:main"
+
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"