Add Bluesky OAuth CLI tool (bsky_oauth.js)
New Bun CLI utility that performs the ATProto OAuth authorization code
flow against a user's PDS. Hosts a temporary localhost callback server,
completes PAR + PKCE + DPoP token exchange via @atproto/oauth-client-node,
and prints the resulting DPoP-bound access token.
Also adds hosted client metadata (docs/client-metadata.json) for
https://v-it.org and updates README with usage instructions.