Fix nginx config for Pancake pretty URLs and static assets

- Update pancake/third_party alias path to use correct NIXPACKS_PHP_ROOT_DIR
- Add proper pretty URL handling with @pancake_fallback location
- Fix SCRIPT_FILENAME to use $document_root instead of $realpath_root
- Enables Apache .htaccess equivalent functionality in nginx

This resolves issues where:
- Static assets in pancake/third_party were returning 404
- Pretty URLs without index.php were not working correctly
- Pancake application routing was broken

nginx.template.conf

@@ -82,7 +82,7 @@ http {
 
         # Static assets for pancake/third_party
         location /pancake/third_party {
-            alias /var/www/html/pancake/third_party;
+            alias ${NIXPACKS_PHP_ROOT_DIR}/pancake/third_party;
             expires 1y;
             add_header Cache-Control "public, immutable";
 
@@ -93,16 +93,22 @@ http {
             }
         }
 
-        # PHP application for /pancake
+        # PHP application for /pancake with pretty URLs
         location /pancake {
-            try_files $uri $uri/ /pancake/index.php?$query_string;
+            # First try to serve the requested file/directory, then fallback to index.php
+            try_files $uri $uri/ @pancake_fallback;
+        }
+
+        # Fallback location for Pancake pretty URLs
+        location @pancake_fallback {
+            rewrite ^.*$ /pancake/index.php last;
         }
 
         # Handle PHP files
 
         location ~ \.php$ {
             fastcgi_pass 127.0.0.1:9000;
-            fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
+            fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
             include $!{nginx}/conf/fastcgi_params;
             include $!{nginx}/conf/fastcgi.conf;
         }