Implement Mihomo external-controller support in configuration and gateway

- Added optional Mihomo configuration fields in `config.compose.yaml` and `config.example.yaml` for enhanced integration with the Mihomo external-controller.
- Updated the `Gateway` to handle Mihomo API requests, including proxying and error handling for Mihomo-specific endpoints.
- Enhanced the documentation in `GATEWAY_RUN.md` to guide users on configuring Mihomo integration.
- Introduced new utility functions in the web client for interacting with Mihomo API endpoints, improving the overall user experience.
- Updated the sidebar in the Svelte components to include a link to the Mihomo section, enhancing navigation.

config.compose.yaml

@@ -8,3 +8,7 @@ trusted_proxies: []
 servers:
   - alias: main_srv
     base_url: http://host.docker.internal:9091
+    # Раскомментируйте при настройке Mihomo и общей сети с контейнером mihomo:
+    # mihomo_base_url: http://mihomo:9090
+    # или: mihomo_base_url_env: MIHOMO_CONTROLLER_URL
+    # mihomo_authorization_env: TELEMT_MIHOMO_AUTH