feat: public_port for managed databases — opt-in 0.0.0.0 bind

Managed databases have always published their port on 127.0.0.1 only.
public_port opts into binding on all interfaces so the database is
reachable off-host. Toggling via PUT recreates the container — the
named data volume survives.

- create accepts public_port; PUT /databases/{id} toggles it
- external rows reject the flag (no container exists)
- CLI: databases create --public, databases update --public/--public=false
- MCP: databases_update tool; UI: create checkbox + per-row toggle

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

llms.txt

@@ -22,6 +22,7 @@ Base URL: `https://<host>/api/v1`. OpenAPI: `docs/api/openapi.yaml`.
 - **Clone & move**: `POST /services/{id}/clone` `{name?, project_id?, environment?}` copies config, volumes, domains, access gates, and variables (secret ciphertext verbatim; clone starts stopped). `POST /services/{id}/move` `{project_id}` re-parents a service — both require ownership of source and target; name conflicts → `CONFLICT`. Cloned domains are verbatim copies: the same hostname on two services makes routing ambiguous.
 - **Registries**: `GET|POST /registries`, `PUT|DELETE /registries/{id}` — owner-scoped private-image pull credentials, encrypted at rest, never returned (`has_password` signals presence). `host` matched against the image reference on image deploys (`docker.io` for Docker Hub; scheme/case normalized). Empty `password` on update keeps the stored credential.
 - **External databases**: `POST /databases/register-external` (probes first; `{name,type,host,port,database,username,password,ssl}`), `POST /databases/test-connection` (ad-hoc probe → `{ok,latency_ms,error}`), `POST /databases/{id}/test-connection` (re-probe with stored credentials). Rows carry `provider:"external"` + `external{host,port,database,username,has_password,ssl}`; passwords encrypted at rest, never returned. Lifecycle actions and backups reject external rows — no container exists.
+- **Public DB port**: managed databases bind `127.0.0.1` by default; `public_port:true` on create or `PUT /databases/{id} {public_port}` binds `0.0.0.0`. Toggling recreates the container — the data volume persists.
 - **Identifiers**: all ids are UUIDs. Tokens: `cnp_` user PATs, `cagt_` agent onboarding tokens.
 
 ## Core objects