style(proxy,server): 代码风格优化

- headers.go: 添加协议常量 protoHTTP/protoHTTPS
- redirect_rewrite.go: 添加模式常量，修正缩进
- proxy_ssl_test.go: 表格测试字段对齐
- server.go: 添加 ServerModeAuto 分支防御性处理

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/proxy/headers.go

@@ -10,6 +10,12 @@ import (
 	"rua.plus/lolly/internal/netutil"
 )
 
+// 协议常量
+const (
+	protoHTTP  = "http"
+	protoHTTPS = "https"
+)
+
 // ForwardedHeaders 包含 X-Forwarded 系列头信息。
 type ForwardedHeaders struct {
 	ClientIP string // 客户端 IP
@@ -28,9 +34,9 @@ func ExtractForwardedHeaders(ctx *fasthttp.RequestCtx) ForwardedHeaders {
 	clientIP := netutil.ExtractClientIP(ctx)
 	host := string(ctx.Host())
 
-	proto := "http"
+	proto := protoHTTP
 	if ctx.IsTLS() {
-		proto = "https"
+		proto = protoHTTPS
 	}
 
 	return ForwardedHeaders{

internal/proxy/redirect_rewrite.go

@@ -10,19 +10,26 @@ import (
 	"rua.plus/lolly/internal/variable"
 )
 
+// RedirectRewrite 模式常量
+const (
+	redirectModeDefault = "default"
+	redirectModeOff     = "off"
+	redirectModeCustom  = "custom"
+)
+
 // compiledRule 预编译的改写规则
 type compiledRule struct {
 	pattern         *regexp.Regexp // 正则模式，nil 表示非正则匹配
-	exactMatch    string         // 精确匹配前缀（用于 prefix 匹配）
 	replacement     string         // 替换模板（含变量）
+	exactMatch      string         // 精确匹配前缀（用于 prefix 匹配）
 	caseInsensitive bool           // 正则大小写不敏感（~* 前缀）
 }
 
 // RedirectRewriter Location/Refresh 头改写器
 type RedirectRewriter struct {
+	proxyPath string         // 用于 default 模式（当前代理路径）
 	mode      string         // "default" | "off" | "custom"（空字符串视为 default）
 	rules     []compiledRule // 仅 custom 模式预编译
-	proxyPath string         // 用于 default 模式（当前代理路径）
 }
 
 // NewRedirectRewriter 创建改写器
@@ -32,7 +39,7 @@ func NewRedirectRewriter(cfg *config.RedirectRewriteConfig, proxyPath string) (*
 	if cfg == nil {
 		// 未配置时默认启用 default 模式
 		return &RedirectRewriter{
-			mode:      "default",
+			mode:      redirectModeDefault,
 			proxyPath: proxyPath,
 		}, nil
 	}
@@ -43,7 +50,7 @@ func NewRedirectRewriter(cfg *config.RedirectRewriteConfig, proxyPath string) (*
 	}
 
 	// custom 模式：预编译规则
-	if cfg.Mode == "custom" {
+	if cfg.Mode == redirectModeCustom {
 		rules := make([]compiledRule, 0, len(cfg.Rules))
 		for _, rule := range cfg.Rules {
 			cr := compiledRule{
@@ -52,7 +59,7 @@ func NewRedirectRewriter(cfg *config.RedirectRewriteConfig, proxyPath string) (*
 
 			if strings.HasPrefix(rule.Pattern, "~") {
 				// 正则模式
-				patternStr := rule.Pattern
+				var patternStr string
 				if strings.HasPrefix(rule.Pattern, "~*") {
 					cr.caseInsensitive = true
 					patternStr = rule.Pattern[2:]
@@ -80,7 +87,7 @@ func NewRedirectRewriter(cfg *config.RedirectRewriteConfig, proxyPath string) (*
 // Mode 返回当前模式（处理空字符串默认值）
 func (r *RedirectRewriter) Mode() string {
 	if r.mode == "" {
-		return "default"
+		return redirectModeDefault
 	}
 	return r.mode
 }
@@ -136,13 +143,13 @@ func (r *RedirectRewriter) rewriteURL(headerValue string, ctx *fasthttp.RequestC
 	}
 
 	switch r.Mode() {
-	case "off":
+	case redirectModeOff:
 		return headerValue
 
-	case "custom":
+	case redirectModeCustom:
 		return r.rewriteCustom(headerValue, ctx)
 
-	case "default", "":
+	case redirectModeDefault, "":
 		return r.rewriteDefault(headerValue, ctx, targetURL, originalClientHost)
 
 	default:
@@ -154,6 +161,7 @@ func (r *RedirectRewriter) rewriteURL(headerValue string, ctx *fasthttp.RequestC
 // 使用前缀匹配：如果 headerValue 以 targetURL 开头，替换为 replacement + 原路径后缀
 // replacement 使用 originalClientHost 构建："$scheme://originalClientHost/"
 // 例如：targetURL="http://backend:8000", headerValue="http://backend:8000/api/v2/users"
+//
 //	→ 替换为 "$scheme://originalClientHost/api/v2/users"
 func (r *RedirectRewriter) rewriteDefault(headerValue string, ctx *fasthttp.RequestCtx, targetURL string, originalClientHost string) string {
 	if targetURL == "" {
@@ -167,9 +175,9 @@ func (r *RedirectRewriter) rewriteDefault(headerValue string, ctx *fasthttp.Requ
 		// 检查剩余部分是否以合法分隔符开头
 		if len(remaining) == 0 || remaining[0] == '/' || remaining[0] == '?' || remaining[0] == '#' {
 			// 使用客户端原始 host 构建 replacement
-			scheme := "http"
+			scheme := protoHTTP
 			if ctx.IsTLS() {
-				scheme = "https"
+				scheme = protoHTTPS
 			}
 			replacement := scheme + "://" + originalClientHost
 			return replacement + remaining

internal/proxy/redirect_rewrite_test.go

@@ -3,10 +3,9 @@ package proxy
 import (
 	"testing"
 
+	"github.com/valyala/fasthttp"
 	"rua.plus/lolly/internal/config"
 	"rua.plus/lolly/internal/testutil"
-
-	"github.com/valyala/fasthttp"
 )
 
 // TestRedirectRewrite_ExactMatch 测试精确匹配改写

internal/server/server.go

@@ -438,6 +438,9 @@ func (s *Server) Start() error {
 		return s.startVHostMode()
 	case config.ServerModeMultiServer:
 		return s.startMultiServerMode()
+	case config.ServerModeAuto:
+		// auto 模式下 GetMode() 会自动推断，此处为防御性处理
+		return s.startSingleMode()
 	default:
 		// 默认使用单服务器模式
 		return s.startSingleMode()