Enhance Mihomo traffic and memory handling with health check support

- Updated `GATEWAY_RUN.md` to clarify the use of HTTP GET requests for traffic and memory metrics, ensuring compatibility with upstream services.
- Added `testUrl` property to `MihomoProxyEntry` type for health check configuration.
- Refactored Svelte component to implement a delay query function, improving error handling and stability during data retrieval.
- Renamed functions for clarity and improved the polling mechanism for traffic and memory data, enhancing overall performance.

web/src/lib/api/mihomo-types.ts

@@ -8,6 +8,8 @@ export type MihomoProxyEntry = {
 	name?: string;
 	now?: string;
 	all?: string[];
+	/** URL для healthcheck / GET …/delay (если задан в конфиге группы). */
+	testUrl?: string;
 	history?: { time: string; delay: number }[];
 	udp?: boolean;
 	[key: string]: unknown;