fix(proxy): support system proxy fallback and provider-level proxy config

- Remove no_proxy() calls in http_client.rs to allow system proxy fallback
- Add get_for_provider() to build HTTP client with provider-specific proxy
- Update forwarder.rs and stream_check.rs to use provider proxy config
- Fix EditProviderDialog.tsx to include provider.meta in useMemo deps
- Add useEffect in ProviderAdvancedConfig.tsx to sync expand state

Fixes #636
Fixes #583

src-tauri/src/services/stream_check.rs

@@ -190,8 +190,9 @@ impl StreamCheckService {
             .extract_auth(provider)
             .ok_or_else(|| AppError::Message("API Key not found".to_string()))?;
 
-        // 使用全局 HTTP 客户端（已包含代理配置）
-        let client = crate::proxy::http_client::get();
+        // 获取 HTTP 客户端：优先使用供应商单独代理配置，否则使用全局客户端
+        let proxy_config = provider.meta.as_ref().and_then(|m| m.proxy_config.as_ref());
+        let client = crate::proxy::http_client::get_for_provider(proxy_config);
         let request_timeout = std::time::Duration::from_secs(config.timeout_secs);
 
         let model_to_test = Self::resolve_test_model(app_type, provider, config);