Dynamic Client Registration (RFC 7591) — proxy to Hydra admin API.

Hydra's own public DCR lets the registering client pick its grants and audience; this proxy registers through the admin API instead so it can fix them. Hydra's public DCR must stay disabled, or it bypasses this endpoint.

We inject server-side defaults:

• skip_consent: true — MCP clients accessing their own workspace don't need consent
• audience: [AGENTAREA_API_URL] — ensures issued JWTs have the correct audience for validation
• grant_types / scope — so the client can refresh instead of re-authorizing