Fix Caddy prod: use php_fastcgi instead of reverse_proxy for PHP-FPM

PHP-FPM speaks FastCGI protocol, not HTTP. Caddy must use php_fastcgi
directive with file_server and try_files for proper Symfony routing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ansible/caddy.j2

@@ -19,11 +19,13 @@ ticket.e-cosplay.fr {
     }
 
     handle {
-        reverse_proxy localhost:4578 localhost:4579 {
+        root * /var/www/e-ticket/public
+        php_fastcgi localhost:4578 localhost:4579 {
             lb_policy round_robin
-            health_uri /
-            health_interval 10s
+            trusted_proxies private_ranges
         }
+        file_server
+        try_files {path} /index.php?{query}
     }
 
     encode gzip