Inline NATS config via docker-compose configs

Coolify's compose executor rewrites relative bind mounts to a persistent
app dir with no source file, causing docker to auto-create the mount
target as a directory and fail with "not a directory". Delivering the
config through configs.content instead avoids the rewrite entirely and
lets Docker Compose substitute NATS_USER/NATS_PASSWORD at parse time.

docker-compose.yml

@@ -5,10 +5,10 @@ services:
     command: ["-c", "/etc/nats/nats-server.conf"]
     environment:
       - SERVICE_FQDN_NATS_8080
-      - NATS_USER=${NATS_USER}
-      - NATS_PASSWORD=${NATS_PASSWORD}
+    configs:
+      - source: nats-conf
+        target: /etc/nats/nats-server.conf
     volumes:
-      - ./nats-server.conf:/etc/nats/nats-server.conf:ro
       - nats-data:/data
     expose:
       - "4222"
@@ -20,5 +20,30 @@ services:
       timeout: 5s
       retries: 3
 
+configs:
+  nats-conf:
+    content: |
+      server_name: "nats-volcanic"
+
+      port: 4222
+      http_port: 8222
+
+      jetstream {
+        store_dir: "/data"
+        max_memory_store: 256MB
+        max_file_store: 4GB
+      }
+
+      websocket {
+        port: 8080
+        no_tls: true
+      }
+
+      authorization {
+        users = [
+          { user: "${NATS_USER}", password: "${NATS_PASSWORD}" }
+        ]
+      }
+
 volumes:
   nats-data: