```

chore: enhance .gitignore and remove obsolete documentation files

- Reorganize .gitignore with categorized sections for better maintainability
- Add comprehensive ignore patterns for Python, Node.js, databases, logs, and build artifacts
- Add project-specific ignore rules for coordinator, explorer, and deployment files
- Remove outdated documentation: BITCOIN-WALLET-SETUP.md, LOCAL_ASSETS_SUMMARY.md, README-CONTAINER-DEPLOYMENT.md, README-DOMAIN-DEPLOYMENT.md
```

infra/nginx/nginx-assets.conf

@@ -0,0 +1,18 @@
+# Add to /etc/nginx/sites-available/aitbc.conf
+
+# Serve production assets
+location /assets/ {
+    alias /var/www/html/assets/;
+    expires 1y;
+    add_header Cache-Control "public, immutable";
+    add_header X-Content-Type-Options nosniff;
+    
+    # Gzip compression
+    gzip on;
+    gzip_types text/css application/javascript image/svg+xml;
+}
+
+# Security headers
+add_header Referrer-Policy "strict-origin-when-cross-origin" always;
+add_header X-Frame-Options "SAMEORIGIN" always;
+add_header X-Content-Type-Options "nosniff" always;