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/auth/gemini/gemini_auth.go

@@ -10,9 +10,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"net"
 	"net/http"
-	"net/url"
 	"time"
 
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/auth/codex"
@@ -20,9 +18,9 @@ import (
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/config"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/misc"
 	"github.com/router-for-me/CLIProxyAPI/v6/internal/util"
+	"github.com/router-for-me/CLIProxyAPI/v6/sdk/proxyutil"
 	log "github.com/sirupsen/logrus"
 	"github.com/tidwall/gjson"
-	"golang.org/x/net/proxy"
 
 	"golang.org/x/oauth2"
 	"golang.org/x/oauth2/google"
@@ -80,36 +78,16 @@ func (g *GeminiAuth) GetAuthenticatedClient(ctx context.Context, ts *GeminiToken
 	}
 	callbackURL := fmt.Sprintf("http://localhost:%d/oauth2callback", callbackPort)
 
-	// Configure proxy settings for the HTTP client if a proxy URL is provided.
-	proxyURL, err := url.Parse(cfg.ProxyURL)
-	if err == nil {
-		var transport *http.Transport
-		if proxyURL.Scheme == "socks5" {
-			// Handle SOCKS5 proxy.
-			username := proxyURL.User.Username()
-			password, _ := proxyURL.User.Password()
-			auth := &proxy.Auth{User: username, Password: password}
-			dialer, errSOCKS5 := proxy.SOCKS5("tcp", proxyURL.Host, auth, proxy.Direct)
-			if errSOCKS5 != nil {
-				log.Errorf("create SOCKS5 dialer failed: %v", errSOCKS5)
-				return nil, fmt.Errorf("create SOCKS5 dialer failed: %w", errSOCKS5)
-			}
-			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" {
-			// Handle HTTP/HTTPS proxy.
-			transport = &http.Transport{Proxy: http.ProxyURL(proxyURL)}
-		}
-
-		if transport != nil {
-			proxyClient := &http.Client{Transport: transport}
-			ctx = context.WithValue(ctx, oauth2.HTTPClient, proxyClient)
-		}
+	transport, _, errBuild := proxyutil.BuildHTTPTransport(cfg.ProxyURL)
+	if errBuild != nil {
+		log.Errorf("%v", errBuild)
+	} else if transport != nil {
+		proxyClient := &http.Client{Transport: transport}
+		ctx = context.WithValue(ctx, oauth2.HTTPClient, proxyClient)
 	}
 
+	var err error
+
 	// Configure the OAuth2 client.
 	conf := &oauth2.Config{
 		ClientID:     ClientID,