Fixed: #2034

feat(proxy): centralize proxy handling with `proxyutil` package and enhance test coverage

- Added `proxyutil` package to simplify proxy handling across the codebase.
- Refactored various components (`executor`, `cliproxy`, `auth`, etc.) to use `proxyutil` for consistent and reusable proxy logic.
- Introduced support for "direct" proxy mode to explicitly bypass all proxies.
- Updated tests to validate proxy behavior (e.g., `direct`, HTTP/HTTPS, and SOCKS5).
- Enhanced YAML configuration documentation for proxy options.

internal/util/proxy.go

@@ -4,50 +4,25 @@
 package util
 
 import (
-	"context"
-	"net"
 	"net/http"
-	"net/url"
 
 	"github.com/router-for-me/CLIProxyAPI/v6/sdk/config"
+	"github.com/router-for-me/CLIProxyAPI/v6/sdk/proxyutil"
 	log "github.com/sirupsen/logrus"
-	"golang.org/x/net/proxy"
 )
 
 // SetProxy configures the provided HTTP client with proxy settings from the configuration.
 // It supports SOCKS5, HTTP, and HTTPS proxies. The function modifies the client's transport
 // to route requests through the configured proxy server.
 func SetProxy(cfg *config.SDKConfig, httpClient *http.Client) *http.Client {
-	var transport *http.Transport
-	// Attempt to parse the proxy URL from the configuration.
-	proxyURL, errParse := url.Parse(cfg.ProxyURL)
-	if errParse == nil {
-		// Handle different proxy schemes.
-		if proxyURL.Scheme == "socks5" {
-			// Configure SOCKS5 proxy with optional authentication.
-			var proxyAuth *proxy.Auth
-			if proxyURL.User != nil {
-				username := proxyURL.User.Username()
-				password, _ := proxyURL.User.Password()
-				proxyAuth = &proxy.Auth{User: username, Password: password}
-			}
-			dialer, errSOCKS5 := proxy.SOCKS5("tcp", proxyURL.Host, proxyAuth, proxy.Direct)
-			if errSOCKS5 != nil {
-				log.Errorf("create SOCKS5 dialer failed: %v", errSOCKS5)
-				return httpClient
-			}
-			// Set up a custom transport using the SOCKS5 dialer.
-			transport = &http.Transport{
-				DialContext: func(ctx context.Context, network, addr string) (net.Conn, error) {
-					return dialer.Dial(network, addr)
-				},
-			}
-		} else if proxyURL.Scheme == "http" || proxyURL.Scheme == "https" {
-			// Configure HTTP or HTTPS proxy.
-			transport = &http.Transport{Proxy: http.ProxyURL(proxyURL)}
-		}
+	if cfg == nil || httpClient == nil {
+		return httpClient
+	}
+
+	transport, _, errBuild := proxyutil.BuildHTTPTransport(cfg.ProxyURL)
+	if errBuild != nil {
+		log.Errorf("%v", errBuild)
 	}
-	// If a new transport was created, apply it to the HTTP client.
 	if transport != nil {
 		httpClient.Transport = transport
 	}