fix: remove backend/frontend host port mappings from base compose

Docker Compose merges port arrays from base + override files, so the
base 3000:3000 and the prod overlay 127.0.0.1:3000:3000 conflicted.
Removed direct host port mappings from the base — dev traffic already
routes through the Docker nginx on port 80 via the bridge network.
The prod overlay cleanly adds loopback-only mappings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -15,8 +15,8 @@ services:
     build:
       context: ./backend
       dockerfile: Dockerfile.dev
-    ports:
+    # No host port mapping — dev traffic goes through the Docker nginx container.
-      - "3000:3000"
+    # Production overlay maps 127.0.0.1:3000 for the host reverse proxy.
     environment:
       - DATABASE_URL=${DATABASE_URL}
       - REDIS_URL=${REDIS_URL}
@@ -43,8 +43,8 @@ services:
     build:
       context: ./frontend
       dockerfile: Dockerfile.dev
-    ports:
+    # No host port mapping — dev traffic goes through the Docker nginx container.
-      - "5173:5173"
+    # Production overlay maps 127.0.0.1:3001 for the host reverse proxy.
     environment:
       - NODE_ENV=${NODE_ENV}
     volumes: