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/Http/Requests/Admin/ServerSave.php

@@ -40,6 +40,7 @@ class ServerSave extends FormRequest
             'tls.allow_insecure' => 'nullable|boolean',
             'bandwidth.up' => 'nullable|integer',
             'bandwidth.down' => 'nullable|integer',
+            'hop_interval' => 'integer|nullable',
         ],
         'vless' => [
             'tls' => 'required|integer',