fix: improve node filtering by client base_version, set subscription content-type, and add hop_interval support for hysteria2

- Refactor node filtering logic to correctly handle client base_version requirements.
- Set appropriate Content-Type header for subscription responses.
- Add support for hop_interval configuration in hysteria2 node delivery.

app/Models/Server.php

@@ -178,7 +178,8 @@ class Server extends Model
                     'server_name' => ['type' => 'string', 'default' => null],
                     'allow_insecure' => ['type' => 'boolean', 'default' => false]
                 ]
-            ]
+            ],
+            'hop_interval' => ['type' => 'integer', 'default' => null]
         ],
         self::TYPE_TUIC => [
             'version' => ['type' => 'integer', 'default' => 5],