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"`
@@ -58,103 +36,170 @@ func handleGetDashboard(c *gin.Context) {
 		StorageUsed    int64  `json:"storageUsed"`
 	}
 
-	var user model.User
-	if err := database.DB.First(&user, userID).Error; err == nil {
-		subscription.Plan = "基础版"
-		if user.Role == "admin" {
-			subscription.Plan = "管理员"
-		}
-		subscription.Status = "正常"
-		if user.Status == "banned" {
-			subscription.Status = "已禁用"
-		}
-		subscription.ExpireDate = "永久"
-	}
-	subscription.AppCount = int(stats.TotalApplications)
-	subscription.APIQuota = 10000
-	subscription.StorageQuota = 100 * 1024 * 1024
-
-	var apiUsed int64
-	database.DB.Model(&model.ApiUsage{}).Where("user_id = ?", userID).Count(&apiUsed)
-	subscription.APIUsed = int(apiUsed)
-
-	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{},
 	}
 
-	if len(appIDs) > 0 {
-		type DeviceCount struct {
-			DeviceType string
-			Count      int
-		}
-		var deviceCounts []DeviceCount
-		database.DB.Model(&model.UserDevice{}).
-			Select("device_type, COUNT(*) as count").
-			Where("application_id IN ?", appIDs).
-			Group("device_type").
-			Order("count DESC").
-			Find(&deviceCounts)
-
-		provinces := make([]gin.H, 0, len(deviceCounts))
-		for _, dc := range deviceCounts {
-			provinces = append(provinces, gin.H{
-				"name":  dc.DeviceType,
-				"count": dc.Count,
-			})
-		}
-		userDistribution["provinces"] = provinces
-	}
-
 	onlineTrend := make([]gin.H, 0, 30)
-	if len(appIDs) > 0 {
-		type DailyCount struct {
-			Date  string
-			Count int64
-		}
-		var dailyCounts []DailyCount
-
-		dateStart := time.Now().AddDate(0, 0, -29)
-		dateStart = time.Date(dateStart.Year(), dateStart.Month(), dateStart.Day(), 0, 0, 0, 0, dateStart.Location())
-
-		database.DB.Model(&model.DeviceSession{}).
-			Select("DATE(last_heartbeat) as date, COUNT(*) as count").
-			Joins("JOIN user_devices ON device_sessions.device_id = user_devices.id").
-			Where("user_devices.application_id IN ? AND last_heartbeat >= ?", appIDs, dateStart).
-			Group("DATE(last_heartbeat)").
-			Order("date ASC").
-			Find(&dailyCounts)
-
-		countMap := make(map[string]int64)
-		for _, dc := range dailyCounts {
-			countMap[dc.Date] = dc.Count
-		}
-
-		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{
-				"date":  date.Format("01-02"),
-				"value": count,
-			})
-		}
-	} else {
-		for i := 29; i >= 0; i-- {
-			date := time.Now().AddDate(0, 0, -i)
-			onlineTrend = append(onlineTrend, gin.H{
-				"date":  date.Format("01-02"),
-				"value": 0,
-			})
-		}
-	}
-
 	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"
+			if user.Role == "admin" {
+				subscription.Plan = "管理员"
+			}
+			subscription.Status = "正常"
+			if user.Status == "banned" {
+				subscription.Status = "已禁用"
+			}
+			subscription.ExpireDate = "永久"
+		}
+	}()
+
+	go func() {
+		defer wg.Done()
+		var apiUsed int64
+		database.DB.Model(&model.ApiUsage{}).Where("user_id = ?", userID).Count(&apiUsed)
+		subscription.APIUsed = int(apiUsed)
+
+		var storageUsed int64
+		database.DB.Model(&model.StorageUsage{}).Where("user_id = ?", userID).Select("COALESCE(SUM(size), 0)").Scan(&storageUsed)
+		subscription.StorageUsed = storageUsed
+	}()
+
+	go func() {
+		defer wg.Done()
+		if len(appIDs) > 0 {
+			type DeviceCount struct {
+				DeviceType string
+				Count      int
+			}
+			var deviceCounts []DeviceCount
+			database.DB.Model(&model.UserDevice{}).
+				Select("device_type, COUNT(*) as count").
+				Where("application_id IN ?", appIDs).
+				Group("device_type").
+				Order("count DESC").
+				Find(&deviceCounts)
+
+			provinces := make([]gin.H, 0, len(deviceCounts))
+			for _, dc := range deviceCounts {
+				provinces = append(provinces, gin.H{
+					"name":  dc.DeviceType,
+					"count": dc.Count,
+				})
+			}
+			mu.Lock()
+			userDistribution["provinces"] = provinces
+			mu.Unlock()
+		}
+	}()
+
+	go func() {
+		defer wg.Done()
+		if len(appIDs) > 0 {
+			type DailyCount struct {
+				Date  string
+				Count int64
+			}
+			var dailyCounts []DailyCount
+
+			dateStart := time.Now().AddDate(0, 0, -29)
+			dateStart = time.Date(dateStart.Year(), dateStart.Month(), dateStart.Day(), 0, 0, 0, 0, dateStart.Location())
+
+			database.DB.Model(&model.DeviceSession{}).
+				Select("DATE(last_heartbeat) as date, COUNT(*) as count").
+				Joins("JOIN user_devices ON device_sessions.device_id = user_devices.id").
+				Where("user_devices.application_id IN ? AND last_heartbeat >= ?", appIDs, dateStart).
+				Group("DATE(last_heartbeat)").
+				Order("date ASC").
+				Find(&dailyCounts)
+
+			countMap := make(map[string]int64)
+			for _, dc := range dailyCounts {
+				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]
+
+				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)
+				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
+
 	var tickets []model.Ticket
 	database.DB.Where("user_id = ?", userID).Order("created_at DESC").Limit(5).Find(&tickets)
 	for _, ticket := range tickets {