chore(deployment): add docker-compose and nginx setup for production

- Added Dockerfile and nginx.conf for frontend production build.
- Added docker-compose.yml to orchestrate backend and frontend.
- Updated geminiService.ts to support relative API paths via Nginx proxy.
- Updated documentation with deployment instructions for Synology/Docker.

general-market-intelligence/nginx.conf

@@ -0,0 +1,22 @@
+server {
+    listen 80;
+    
+    # 1. Serve React Frontend (Static Files)
+    location / {
+        root /usr/share/nginx/html;
+        index index.html index.htm;
+        try_files $uri $uri/ /index.html; # Support for React Router (SPA)
+    }
+
+    # 2. Proxy API Requests to Backend Container
+    location /api/ {
+        # 'backend' is the service name in docker-compose.yml
+        # Port 3001 is where the Node.js bridge listens
+        proxy_pass http://backend:3001/api/;
+        proxy_http_version 1.1;
+        proxy_set_header Upgrade $http_upgrade;
+        proxy_set_header Connection 'upgrade';
+        proxy_set_header Host $host;
+        proxy_cache_bypass $http_upgrade;
+    }
+}