Add frontend and Caddy to Docker Compose dev environment

Containerize the frontend dev server (Vite) and add a Caddy reverse
proxy for HTTPS termination, replacing the manual local setup. The
Caddy config proxies /api/* to the backend and everything else to the
frontend dev server.

Also simplify start.sh: remove --local Poetry mode, extract
get_compose_cmd helper, and document new services and DEV_HOST env var.

crawler/docker-compose.yml

@@ -1,5 +1,3 @@
-version: "3.8"
-
 services:
   redis:
     image: redis:8
@@ -111,6 +109,37 @@ services:
     networks:
       - rec-network
 
+  frontend:
+    image: node:24-alpine
+    container_name: rec-frontend
+    working_dir: /app
+    ports:
+      - "5173:5173"
+    volumes:
+      - ./frontend:/app
+      - frontend_node_modules:/app/node_modules
+    environment:
+      - DEV_HOST=${DEV_HOST:-localhost}
+    command: sh -c "npm ci && npm run dev -- --host"
+    networks:
+      - rec-network
+
+  caddy:
+    image: caddy:alpine
+    container_name: rec-caddy
+    ports:
+      - "443:443"
+    volumes:
+      - ./frontend/Caddyfile.dev:/etc/caddy/Caddyfile
+      - caddy_data:/data
+    environment:
+      - DEV_HOST=${DEV_HOST:-localhost}
+    depends_on:
+      - frontend
+      - app
+    networks:
+      - rec-network
+
 networks:
   rec-network:
     driver: bridge
@@ -119,3 +148,5 @@ volumes:
   redis_data:
   mysql_data:
   app_venv:
+  frontend_node_modules:
+  caddy_data: