Add PostGIS compose service and update public integration docs.

Wire API services to PostGIS in docker-compose, broaden CORS handling for cross-origin clients, and align developer docs with the production momswap URL.

Made-with: Cursor

README.md

@@ -20,7 +20,9 @@ go test ./...
 go run ./cmd/api
 ```
 
-Server default: `http://localhost:8080`.
+Primary deployed base URL: `https://momswap.produktor.duckdns.org/`.
+
+Local default (for development): `http://localhost:8080`.
 
 Optional environment variables:
 
@@ -35,6 +37,11 @@ Build and run the backend service:
 COMPOSE_BAKE=true docker compose up --build -d
 ```
 
+This starts:
+
+- `db` (`postgis/postgis`) on `5432`
+- `api` on `8080`, wired with `DATABASE_URL` to the `db` service
+
 Stop the service:
 
 ```bash
@@ -52,6 +59,7 @@ Notes:
 - `api` service uses the production `runtime` image target.
 - `api-dev` profile uses the `dev` image target and Docker Compose watch.
 - Build cache is persisted at `.docker/buildx-cache` via `cache_from`/`cache_to`.
+- DB defaults can be overridden via `POSTGRES_DB`, `POSTGRES_USER`, `POSTGRES_PASSWORD`.
 
 ## Frontend
 
@@ -63,7 +71,10 @@ Example:
 go run ./cmd/api
 ```
 
-Then visit `http://localhost:8080/web/`.
+Then visit:
+
+- Production: `https://momswap.produktor.duckdns.org/web/`
+- Local: `http://localhost:8080/web/`
 
 ## API client library