```

chore: refactor logging module, update genesis timestamp, remove model relationships, and reorganize routers

- Rename logging.py to logger.py and update import paths in poa.py and main.py
- Update devnet genesis timestamp to 1766828620
- Remove SQLModel Relationship declarations from Block, Transaction, and Receipt models
- Add SessionDep type alias and get_session dependency in coordinator-api deps
- Reorganize coordinator-api routers: replace explorer/registry with exchange, users, marketplace

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;