feat: add Docker deployment configuration

- Add multi-stage Dockerfile for static build
- Add nginx configuration with COOP/COEP headers for FFmpeg.wasm
- Add .dockerignore for optimized builds
- Enable SharedArrayBuffer support via security headers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

nginx.conf

@@ -0,0 +1,69 @@
+events {
+  worker_connections 1024;
+}
+
+http {
+  include /etc/nginx/mime.types;
+  default_type application/octet-stream;
+
+  # Logging
+  access_log /var/log/nginx/access.log;
+  error_log /var/log/nginx/error.log;
+
+  # Performance
+  sendfile on;
+  tcp_nopush on;
+  tcp_nodelay on;
+  keepalive_timeout 65;
+  types_hash_max_size 2048;
+
+  # Gzip compression
+  gzip on;
+  gzip_vary on;
+  gzip_proxied any;
+  gzip_comp_level 6;
+  gzip_types text/plain text/css text/xml text/javascript application/json application/javascript application/xml+rss application/rss+xml font/truetype font/opentype application/vnd.ms-fontobject image/svg+xml;
+
+  server {
+    listen 80;
+    server_name _;
+
+    root /usr/share/nginx/html;
+    index index.html;
+
+    # Security headers
+    add_header X-Frame-Options "SAMEORIGIN" always;
+    add_header X-Content-Type-Options "nosniff" always;
+    add_header X-XSS-Protection "1; mode=block" always;
+    add_header Referrer-Policy "no-referrer-when-downgrade" always;
+
+    # IMPORTANT: Headers required for FFmpeg.wasm SharedArrayBuffer support
+    add_header Cross-Origin-Embedder-Policy "require-corp" always;
+    add_header Cross-Origin-Opener-Policy "same-origin" always;
+
+    # Cache static assets (including WASM files)
+    location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot|wasm)$ {
+      expires 1y;
+      add_header Cache-Control "public, immutable";
+      # Ensure COOP/COEP headers are also set for static assets
+      add_header Cross-Origin-Embedder-Policy "require-corp" always;
+      add_header Cross-Origin-Opener-Policy "same-origin" always;
+    }
+
+    # Serve index.html for all routes (SPA)
+    location / {
+      try_files $uri $uri/ /index.html;
+      add_header Cache-Control "no-cache";
+      # Ensure COOP/COEP headers for HTML
+      add_header Cross-Origin-Embedder-Policy "require-corp" always;
+      add_header Cross-Origin-Opener-Policy "same-origin" always;
+    }
+
+    # Health check endpoint
+    location /health {
+      access_log off;
+      return 200 "healthy\n";
+      add_header Content-Type text/plain;
+    }
+  }
+}