feat: replace Nginx with Caddy for automatic SSL management

- Add Caddyfile with automatic HTTPS configuration
- Add Dockerfile.caddy for frontend build with Caddy
- Update docker-compose.yml to use Caddy service
- Update DEPLOY.md with simplified deployment instructions

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.yml

@@ -26,17 +26,18 @@ services:
     networks:
       - gala-network
 
-  nginx:
+  caddy:
     build:
       context: .
-      dockerfile: deploy/Dockerfile.frontend
-    container_name: gala-nginx
+      dockerfile: deploy/Dockerfile.caddy
+    container_name: gala-caddy
     restart: unless-stopped
     ports:
       - "80:80"
       - "443:443"
     volumes:
-      - ./deploy/ssl:/etc/nginx/ssl:ro
+      - caddy_data:/data
+      - caddy_config:/config
     depends_on:
       - server
     networks:
@@ -44,6 +45,8 @@ services:
 
 volumes:
   redis_data:
+  caddy_data:
+  caddy_config:
 
 networks:
   gala-network: