chore(deploy): Docker production config, nginx gzip/cache, deploy docs

- docker-compose.yml: restart always, env_file, named volume, start_period
- frontend/nginx.conf: gzip compression, cache headers for assets, no-cache for SW
- Makefile: add prod-down and prod-logs targets
- docs/DEPLOY.md: Dokploy + Cloudflare Tunnel deploy instructions

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

frontend/nginx.conf

@@ -3,10 +3,38 @@ server {
     root /usr/share/nginx/html;
     index index.html;
 
+    # Gzip compression
+    gzip on;
+    gzip_vary on;
+    gzip_proxied any;
+    gzip_min_length 256;
+    gzip_types
+        text/plain
+        text/css
+        text/javascript
+        application/javascript
+        application/json
+        application/manifest+json
+        image/svg+xml;
+
+    # SPA routing
     location / {
         try_files $uri $uri/ /index.html;
     }
 
+    # Static assets - long cache
+    location /assets {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+    }
+
+    # Service worker - no cache
+    location /sw.js {
+        expires off;
+        add_header Cache-Control "no-store, no-cache, must-revalidate";
+    }
+
+    # API proxy
     location /api {
         proxy_pass http://backend:8000;
         proxy_set_header Host $host;