perf: 优化 Dashboard 接口性能，并行执行数据库查询

- 使用 goroutine 并行执行 8 个数据库查询
- 将串行查询改为并行，显著减少响应时间
- 使用 sync.WaitGroup 和 sync.Mutex 保证线程安全

backend/internal/router/admin/dashboard.go

@@ -1,6 +1,7 @@
 package admin
 
 import (
+	"sync"
 	"time"
 	"verification-platform-backend/internal/database"
 	"verification-platform-backend/internal/model"
@@ -23,29 +24,6 @@ func handleGetDashboard(c *gin.Context) {
 		MonthlyRevenue    float64 `json:"monthlyRevenue"`
 	}
 
-	database.DB.Model(&model.Application{}).Where("user_id = ?", userID).Count(&stats.TotalApplications)
-
-	var appIDs []uint
-	database.DB.Model(&model.Application{}).Where("user_id = ?", userID).Pluck("id", &appIDs)
-	if len(appIDs) > 0 {
-		database.DB.Model(&model.AppUser{}).Where("application_id IN ?", appIDs).Count(&stats.TotalUsers)
-	}
-
-	database.DB.Model(&model.Card{}).Where("creator_id = ?", userID).Count(&stats.TotalCards)
-
-	var monthlyRevenue float64
-	if len(appIDs) > 0 {
-		var appUserIDs []uint
-		database.DB.Model(&model.AppUser{}).Where("application_id IN ?", appIDs).Pluck("id", &appUserIDs)
-		if len(appUserIDs) > 0 {
-			database.DB.Model(&model.RechargeRecord{}).
-				Where("user_id IN ? AND status = ? AND created_at >= ?", appUserIDs, "success", time.Now().AddDate(0, -1, 0)).
-				Select("COALESCE(SUM(amount), 0)").
-				Scan(&monthlyRevenue)
-		}
-	}
-	stats.MonthlyRevenue = monthlyRevenue
-
 	var subscription struct {
 		Plan           string `json:"plan"`
 		Status         string `json:"status"`
@@ -58,6 +36,57 @@ func handleGetDashboard(c *gin.Context) {
 		StorageUsed    int64  `json:"storageUsed"`
 	}
 
+	userDistribution := gin.H{
+		"provinces": []gin.H{},
+		"overseas":  []gin.H{},
+	}
+
+	onlineTrend := make([]gin.H, 0, 30)
+	recentTickets := make([]gin.H, 0, 5)
+
+	var appIDs []uint
+	database.DB.Model(&model.Application{}).Where("user_id = ?", userID).Pluck("id", &appIDs)
+
+	var wg sync.WaitGroup
+	var mu sync.Mutex
+
+	wg.Add(8)
+
+	go func() {
+		defer wg.Done()
+		database.DB.Model(&model.Application{}).Where("user_id = ?", userID).Count(&stats.TotalApplications)
+	}()
+
+	go func() {
+		defer wg.Done()
+		database.DB.Model(&model.Card{}).Where("creator_id = ?", userID).Count(&stats.TotalCards)
+	}()
+
+	go func() {
+		defer wg.Done()
+		if len(appIDs) > 0 {
+			database.DB.Model(&model.AppUser{}).Where("application_id IN ?", appIDs).Count(&stats.TotalUsers)
+		}
+	}()
+
+	go func() {
+		defer wg.Done()
+		if len(appIDs) > 0 {
+			var appUserIDs []uint
+			database.DB.Model(&model.AppUser{}).Where("application_id IN ?", appIDs).Pluck("id", &appUserIDs)
+			if len(appUserIDs) > 0 {
+				var revenue float64
+				database.DB.Model(&model.RechargeRecord{}).
+					Where("user_id IN ? AND status = ? AND created_at >= ?", appUserIDs, "success", time.Now().AddDate(0, -1, 0)).
+					Select("COALESCE(SUM(amount), 0)").
+					Scan(&revenue)
+				stats.MonthlyRevenue = revenue
+			}
+		}
+	}()
+
+	go func() {
+		defer wg.Done()
 		var user model.User
 		if err := database.DB.First(&user, userID).Error; err == nil {
 			subscription.Plan = "基础版"
@@ -70,10 +99,10 @@ func handleGetDashboard(c *gin.Context) {
 			}
 			subscription.ExpireDate = "永久"
 		}
-	subscription.AppCount = int(stats.TotalApplications)
-	subscription.APIQuota = 10000
-	subscription.StorageQuota = 100 * 1024 * 1024
+	}()
 
+	go func() {
+		defer wg.Done()
 		var apiUsed int64
 		database.DB.Model(&model.ApiUsage{}).Where("user_id = ?", userID).Count(&apiUsed)
 		subscription.APIUsed = int(apiUsed)
@@ -81,12 +110,10 @@ func handleGetDashboard(c *gin.Context) {
 		var storageUsed int64
 		database.DB.Model(&model.StorageUsage{}).Where("user_id = ?", userID).Select("COALESCE(SUM(size), 0)").Scan(&storageUsed)
 		subscription.StorageUsed = storageUsed
+	}()
 
-	userDistribution := gin.H{
-		"provinces": []gin.H{},
-		"overseas":  []gin.H{},
-	}
-
+	go func() {
+		defer wg.Done()
 		if len(appIDs) > 0 {
 			type DeviceCount struct {
 				DeviceType string
@@ -107,10 +134,14 @@ func handleGetDashboard(c *gin.Context) {
 					"count": dc.Count,
 				})
 			}
+			mu.Lock()
 			userDistribution["provinces"] = provinces
+			mu.Unlock()
 		}
+	}()
 
-	onlineTrend := make([]gin.H, 0, 30)
+	go func() {
+		defer wg.Done()
 		if len(appIDs) > 0 {
 			type DailyCount struct {
 				Date  string
@@ -134,27 +165,41 @@ func handleGetDashboard(c *gin.Context) {
 				countMap[dc.Date] = dc.Count
 			}
 
+			trend := make([]gin.H, 0, 30)
 			for i := 29; i >= 0; i-- {
 				date := time.Now().AddDate(0, 0, -i)
 				dateStr := date.Format("2006-01-02")
 				count := countMap[dateStr]
 
-			onlineTrend = append(onlineTrend, gin.H{
+				trend = append(trend, gin.H{
 					"date":  date.Format("01-02"),
 					"value": count,
 				})
 			}
+			mu.Lock()
+			onlineTrend = trend
+			mu.Unlock()
 		} else {
+			trend := make([]gin.H, 0, 30)
 			for i := 29; i >= 0; i-- {
 				date := time.Now().AddDate(0, 0, -i)
-			onlineTrend = append(onlineTrend, gin.H{
+				trend = append(trend, gin.H{
 					"date":  date.Format("01-02"),
 					"value": 0,
 				})
 			}
+			mu.Lock()
+			onlineTrend = trend
+			mu.Unlock()
 		}
+	}()
+
+	wg.Wait()
+
+	subscription.AppCount = int(stats.TotalApplications)
+	subscription.APIQuota = 10000
+	subscription.StorageQuota = 100 * 1024 * 1024
 
-	recentTickets := make([]gin.H, 0, 5)
 	var tickets []model.Ticket
 	database.DB.Where("user_id = ?", userID).Order("created_at DESC").Limit(5).Find(&tickets)
 	for _, ticket := range tickets {