- Migrate $protocol_settings['key'] to data_get($protocol_settings, 'key') across General, SingBox, Shadowrocket, Surfboard, QuantumultX
- Prevents PHP 8 Undefined array key fatal errors when optional protocol_settings fields are missing
- Same class of bug that caused #735
- Unify protocol filter configuration to client.type.field (dot-path, three-segment) format, support strict whitelist mode
- Refactor AbstractProtocol and all protocol classes for more flexible and maintainable subscription delivery
- Change payment callback logic: use origin_url concatenation instead of return_url for more accurate redirects
- Add HookManager::filter('client.subscribe.servers') hook in ClientController::subscribe()
- Allow plugins to inject custom servers into subscription responses
- Update protocol classes to support extended server configurations
- Enable dynamic server list modification before protocol processing
- 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.
