improvement: docker infrastructure overhauled.

infrastructure/env.staging.example

@@ -0,0 +1,13 @@
+# Copy to .env.staging next to docker-compose.staging.yml (optional).
+# Used only for compose variable substitution (build args, host port).
+
+STAGING_HTTP_PORT=8088
+
+# Public URLs baked into the frontend image at build time — must match how users open the app.
+STAGING_NEXT_PUBLIC_API_URL=http://178.131.50.201:8088/api
+STAGING_NEXT_PUBLIC_APP_URL=http://178.131.50.201:8088
+STAGING_NEXT_PUBLIC_APP_NAME=Dyolink
+
+# Change the IP/port if your server address differs.
+
+# Registry / pull-only deploy (see deploy.registry.env.example + docker-compose.registry.yml).