fix(deploy): re-resolve php upstream on each request to survive container restarts

Using resolver 127.0.0.11 (Docker internal DNS) with set $php_upstream
forces nginx to re-resolve the php hostname dynamically instead of caching
the IP at startup — eliminates 502 after php container is recreated.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

deploy/nginx/site.conf

@@ -12,13 +12,17 @@ server {
         try_files $uri $uri/ /index.php?$query_string;
     }
 
+    # Docker DNS resolver — re-resolves php hostname on each request
+    resolver 127.0.0.11 valid=5s;
+
     location ~ \.php$ {
         include fastcgi_params;
         fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
         # SSL терминирован на host nginx — передаём это в PHP
         fastcgi_param HTTPS on;
         fastcgi_param HTTP_X_FORWARDED_PROTO https;
-        fastcgi_pass php:9000;
+        set $php_upstream php:9000;
+        fastcgi_pass $php_upstream;
         fastcgi_hide_header Cache-Control;
         add_header Cache-Control "no-store, no-cache, must-revalidate, private" always;
     }