chore: add Docker/nginx setup for Coolify deployment

- Add multi-stage Dockerfile (Node 24 + pnpm builder, nginx:alpine server)
- Add nginx.conf with SPA routing and asset caching
- Remove netlify.toml

nginx.conf

@@ -0,0 +1,23 @@
+server {
+    listen 80;
+    server_name _;
+    root /usr/share/nginx/html;
+    index index.html;
+
+    gzip on;
+    gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript image/svg+xml;
+    gzip_min_length 1024;
+
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+
+    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot|webmanifest)$ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+    }
+
+    location = /index.html {
+        add_header Cache-Control "no-cache";
+    }
+}