Fix nginx configuration syntax errors

- Move proxy_set_header directives inside location blocks
- Add DNS resolver for dynamic upstream resolution
- Improve fallback configuration in docker-compose
- Add config validation before starting nginx

This should resolve the nginx startup failures.

docker-compose.zero-downtime-fixed.yml

@@ -31,8 +31,11 @@ services:
         # Remove default nginx configuration files to prevent conflicts
         rm -rf /etc/nginx/conf.d/*
         
-        if [ ! -f /etc/nginx/nginx.conf ]; then
-          echo 'Creating fallback nginx configuration...'
+        # Test the main config first
+        if nginx -t -c /etc/nginx/nginx.conf 2>/dev/null; then
+          echo 'Using main nginx configuration'
+        else
+          echo 'Main config failed, creating fallback nginx configuration...'
           cat > /etc/nginx/nginx.conf << 'EOF'
       events {
           worker_connections 1024;
@@ -56,6 +59,9 @@ services:
                   proxy_set_header X-Real-IP \$remote_addr;
                   proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;
                   proxy_set_header X-Forwarded-Proto \$scheme;
+                  proxy_connect_timeout 5s;
+                  proxy_send_timeout 60s;
+                  proxy_read_timeout 60s;
               }
           }
       }

nginx-zero-downtime.conf

@@ -9,11 +9,25 @@ http {
         server portfolio-app-2:3000 max_fails=3 fail_timeout=30s;
     }
     
+    # Resolver for dynamic upstream resolution
+    resolver 127.0.0.11 valid=10s;
+
     # Main server
     server {
         listen 80;
         server_name _;
 
+        # Health check endpoint
+        location /health {
+            access_log off;
+            return 200 "healthy\n";
+            add_header Content-Type text/plain;
+        }
+
+        # Main location
+        location / {
+            proxy_pass http://portfolio_backend;
+            
             # Proxy settings
             proxy_set_header Host $host;
             proxy_set_header X-Real-IP $remote_addr;
@@ -30,17 +44,6 @@ http {
             proxy_buffer_size 4k;
             proxy_buffers 8 4k;
             
-        # Health check endpoint
-        location /health {
-            access_log off;
-            return 200 "healthy\n";
-            add_header Content-Type text/plain;
-        }
-
-        # Main location
-        location / {
-            proxy_pass http://portfolio_backend;
-            
             # Health check for upstream
             proxy_next_upstream error timeout invalid_header http_500 http_502 http_503 http_504;
             proxy_next_upstream_tries 2;
@@ -50,6 +53,13 @@ http {
         # Static files caching
         location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$ {
             proxy_pass http://portfolio_backend;
+            
+            # Proxy settings
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+            
             expires 1y;
             add_header Cache-Control "public, immutable";
         }