feat: Implement core backend API server with configuration, S2A proxy, and mail service APIs, and introduce EmailConfig frontend page.

backend/cmd/main.go

@@ -344,16 +344,19 @@ func handleMailServices(w http.ResponseWriter, r *http.Request) {
 	switch r.Method {
 	case "GET":
 		services := mail.GetServices()
-		safeServices := make([]map[string]interface{}, len(services))
+		// 返回完整配置（包括 token）供前端加载
+		result := make([]map[string]interface{}, len(services))
 		for i, s := range services {
-			safeServices[i] = map[string]interface{}{
+			result[i] = map[string]interface{}{
 				"name":       s.Name,
-				"api_base":  s.APIBase,
-				"has_token": s.APIToken != "",
+				"apiBase":    s.APIBase,
+				"apiToken":   s.APIToken,
 				"domain":     s.Domain,
+				"emailPath":  s.EmailPath,
+				"addUserApi": s.AddUserAPI,
 			}
 		}
-		api.Success(w, safeServices)
+		api.Success(w, result)
 	case "POST":
 		var req struct {
 			Services []struct {
@@ -393,7 +396,7 @@ func handleMailServices(w http.ResponseWriter, r *http.Request) {
 			})
 		}
 
-		// 更新邮箱服务配置
+		// 更新邮箱服务配置（内存）
 		mail.Init(services)
 
 		// 保存到全局配置
@@ -401,6 +404,14 @@ func handleMailServices(w http.ResponseWriter, r *http.Request) {
 			config.Global.MailServices = services
 		}
 
+		// 持久化到数据库
+		if database.Instance != nil {
+			jsonData, _ := json.Marshal(services)
+			if err := database.Instance.SetConfig("mail_services", string(jsonData)); err != nil {
+				logger.Error(fmt.Sprintf("保存邮箱配置到数据库失败: %v", err), "", "mail")
+			}
+		}
+
 		logger.Success(fmt.Sprintf("邮箱服务配置已保存: %d 个服务", len(services)), "", "mail")
 		for _, s := range services {
 			logger.Info(fmt.Sprintf("  - %s (%s) @ %s", s.Name, s.Domain, s.APIBase), "", "mail")
@@ -483,8 +494,15 @@ func handleTestMailService(w http.ResponseWriter, r *http.Request) {
 	}
 
 	// 判断结果
-	if result.Code == 200 || strings.Contains(result.Message, "exist") {
-		logger.Success(fmt.Sprintf("邮箱服务测试成功: %s", req.Name), "", "mail")
+	// code 200 = 创建成功
+	// code 501 且消息包含"已存在" = 邮箱已存在，说明连接正常
+	isSuccess := result.Code == 200 ||
+		strings.Contains(result.Message, "exist") ||
+		strings.Contains(result.Message, "已存在") ||
+		(result.Code == 501 && strings.Contains(result.Message, "邮箱"))
+
+	if isSuccess {
+		logger.Success(fmt.Sprintf("邮箱服务测试成功: %s (邮箱已存在或创建成功)", req.Name), "", "mail")
 		api.Success(w, map[string]interface{}{
 			"connected": true,
 			"message":   "邮箱服务连接成功",

frontend/src/pages/EmailConfig.tsx

@@ -5,21 +5,36 @@ import { useConfig } from '../hooks/useConfig'
 import type { MailServiceConfig } from '../types'
 
 export default function EmailConfig() {
-    const { config, updateEmailConfig } = useConfig()
+    const { updateEmailConfig } = useConfig()
     const toast = useToast()
 
     const [saved, setSaved] = useState(false)
     const [saving, setSaving] = useState(false)
-    const [services, setServices] = useState<MailServiceConfig[]>(config.email?.services || [])
+    const [loading, setLoading] = useState(true)
+    const [services, setServices] = useState<MailServiceConfig[]>([])
     const [testingIndex, setTestingIndex] = useState<number | null>(null)
     const [testResults, setTestResults] = useState<Record<number, { success: boolean; message: string }>>({})
 
-    // 同步配置变化
+    // 从后端加载配置
     useEffect(() => {
-        if (config.email?.services) {
-            setServices(config.email.services)
+        const loadConfig = async () => {
+            try {
+                const res = await fetch('/api/mail/services')
+                if (res.ok) {
+                    const data = await res.json()
+                    if (data.code === 0 && Array.isArray(data.data)) {
+                        setServices(data.data)
+                        updateEmailConfig({ services: data.data })
                     }
-    }, [config.email?.services])
+                }
+            } catch (e) {
+                console.error('加载邮箱配置失败:', e)
+            }
+            setLoading(false)
+        }
+        loadConfig()
+        // eslint-disable-next-line react-hooks/exhaustive-deps
+    }, [])
 
     const handleSave = async () => {
         if (services.length === 0) {
@@ -146,6 +161,14 @@ export default function EmailConfig() {
             </div>
 
             {/* Service Cards */}
+            {loading ? (
+                <Card>
+                    <CardContent className="flex items-center justify-center py-8">
+                        <Loader2 className="h-6 w-6 animate-spin text-slate-400" />
+                        <span className="ml-2 text-slate-500">加载中...</span>
+                    </CardContent>
+                </Card>
+            ) : (
                 <div className="space-y-4">
                     {services.map((service, index) => (
                         <Card key={index}>
@@ -246,6 +269,7 @@ export default function EmailConfig() {
                         </Card>
                     ))}
                 </div>
+            )}
 
             {/* Help Info */}
             <Card>