fix(cors): enable credentials, enumerate origins for PouchDB sessions

PouchDB-style apps call fetch with credentials: 'include' to maintain
the CouchDB _session cookie. Without Access-Control-Allow-Credentials:
true in the preflight response, the browser silently blocks the
mutating request (Firefox HAR shows status 0, _securityState insecure).
Switching cors/credentials to true forces enumerating allowed origins
(wildcard + credentials is forbidden by the CORS spec). Listed are the
common Vite/Next/etc. local dev ports plus the vaquant.at frontend.

README.md

@@ -30,7 +30,16 @@ If the init logs show CORS errors, you can re-trigger only that step by redeploy
 
 ## CORS
 
-Wildcard origin (`*`) with `credentials = false` — the only browser-spec-legal combination with a wildcard. For credentialed auth from the browser, edit the `put_config cors origins`/`credentials` lines in `docker-compose.yml`.
+`credentials = true` with an explicit origin list — required for PouchDB-style cookie sessions (`POST /_session`). Wildcard origin is incompatible with credentials per the CORS spec, so allowed origins must be enumerated.
+
+Update the `put_config cors origins` line in `docker-compose.yml` (comma-separated, no spaces) and redeploy when you add a new frontend. Or apply live:
+
+```
+curl -fsS -X PUT -u admin:$PASS \
+  -H "Content-Type: application/json" \
+  https://couch.apoena.dev/_node/_local/_config/cors/origins \
+  -d '"http://localhost:8080,https://new-frontend.example.com"'
+```
 
 ## Hardcoded values (cloning to another Coolify resource)