feat: add Docker deployment (backend:18889, frontend:18888)

- Dockerfile.backend: Python 3.11 + FastAPI + uvicorn
- Dockerfile.frontend: Node 20 build + Nginx serve
- docker-compose.yml: orchestration with data volume mount
- nginx.conf: API/WebSocket proxy to backend
- web/backend/requirements.txt: Python dependencies
- .dockerignore: exclude venv/node_modules/data from build

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

nginx.conf

@@ -0,0 +1,43 @@
+server {
+    listen 18888;
+    server_name _;
+
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Gzip compression
+    gzip on;
+    gzip_types text/plain text/css application/json application/javascript text/xml;
+    gzip_min_length 1000;
+
+    # API proxy to backend
+    location /api/ {
+        proxy_pass http://backend:18889;
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+    }
+
+    # WebSocket proxy to backend
+    location /ws/ {
+        proxy_pass http://backend:18889;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection "upgrade";
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_read_timeout 86400;
+    }
+
+    # Vue Router history mode - serve index.html for all routes
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+
+    # Cache static assets
+    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
+        expires 30d;
+        add_header Cache-Control "public, immutable";
+    }
+}