fix(stability): 修复慢查询雪崩隐患、系统配置死锁与提号翻页错误

- 消除 system_configs 写锁争抢：使用读写锁与启动预热将默认配置初始化收敛为单例，杜绝读请求开事务导致的 Lock wait timeout exceeded
- 强化财务看板缓存：将 Redis 缓存有效期由 1 分钟延长为 5 分钟，接入 singleflight.Group 防并发击穿
- 修复提号列表 GORM 翻页 Bug：分离 Count 查询与列表查询构建，避免重复 Join 导致的 Error 1066
- 生产环境资源加固：docker-compose.prod.yml 中 MySQL 资源限制提升至 2.0 核 CPU、2G 内存
- 补充 systemconfig 并发测试与 pickup 分页 Count 回归测试

backend/internal/modules/adminfinance/dashboard.go

@@ -2,6 +2,7 @@ package adminfinance
 
 import (
 	"context"
+	"errors"
 	"sync"
 
 	"hfb_sys/backend/internal/timeutil"
@@ -11,6 +12,26 @@ func (r *Repository) Dashboard(ctx context.Context, query DashboardQuery) (*Dash
 	if cached := r.loadDashboardCache(ctx, query); cached != nil {
 		return cached, nil
 	}
+
+	key := r.dashboardCacheKey(query)
+	val, err, _ := r.sfGroup.Do(key, func() (any, error) {
+		// 在 singleflight 内部二次检查缓存，避免排队等待的并发请求重复执行大聚合
+		if cached := r.loadDashboardCache(ctx, query); cached != nil {
+			return cached, nil
+		}
+		return r.calculateDashboard(ctx, query)
+	})
+	if err != nil {
+		return nil, err
+	}
+	res, ok := val.(*DashboardDTO)
+	if !ok {
+		return nil, errors.New("invalid dashboard result type")
+	}
+	return res, nil
+}
+
+func (r *Repository) calculateDashboard(ctx context.Context, query DashboardQuery) (*DashboardDTO, error) {
 	// 各板块的读取互不依赖。并行执行能避免单个请求串行等待二十余条统计 SQL，
 	// 首次打开或缓存失效时仍可尽快返回；每个查询继续复用 GORM 的连接池。
 	var (

backend/internal/modules/adminfinance/dashboard_cache.go

@@ -7,7 +7,7 @@ import (
 	"time"
 )
 
-const dashboardCacheTTL = time.Minute
+const dashboardCacheTTL = 5 * time.Minute
 
 func (r *Repository) dashboardCacheKey(query DashboardQuery) string {
 	return fmt.Sprintf("admin-finance:dashboard:v1:%d:%d", query.StartDate.Unix(), query.EndDate.Unix())

backend/internal/modules/adminfinance/dashboard_test.go

@@ -1,6 +1,8 @@
 package adminfinance
 
 import (
+	"sync"
+	"sync/atomic"
 	"testing"
 	"time"
 
@@ -369,3 +371,33 @@ func TestSummaryFromDailyRowsPreservesDashboardTotals(t *testing.T) {
 		t.Fatalf("订单状态汇总错误: %+v", summary)
 	}
 }
+
+func TestDashboardCacheKeyAndSingleflight(t *testing.T) {
+	repo := NewRepository(nil)
+	q := DashboardQuery{
+		StartDate: time.Date(2026, 9, 1, 0, 0, 0, 0, time.UTC),
+		EndDate:   time.Date(2026, 9, 7, 0, 0, 0, 0, time.UTC),
+	}
+	key := repo.dashboardCacheKey(q)
+	if key == "" {
+		t.Fatal("cache key should not be empty")
+	}
+
+	var callCount atomic.Int32
+	var wg sync.WaitGroup
+	for i := 0; i < 10; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			_, _, _ = repo.sfGroup.Do(key, func() (any, error) {
+				callCount.Add(1)
+				time.Sleep(20 * time.Millisecond)
+				return &DashboardDTO{}, nil
+			})
+		}()
+	}
+	wg.Wait()
+	if count := callCount.Load(); count != 1 {
+		t.Fatalf("singleflight 并发合并失败: got %d, want 1", count)
+	}
+}

backend/internal/modules/adminfinance/repository.go

@@ -2,12 +2,14 @@ package adminfinance
 
 import (
 	"github.com/redis/go-redis/v9"
+	"golang.org/x/sync/singleflight"
 	"gorm.io/gorm"
 )
 
 type Repository struct {
-	db    *gorm.DB
-	redis *redis.Client
+	db      *gorm.DB
+	redis   *redis.Client
+	sfGroup singleflight.Group
 }
 
 func NewRepository(db *gorm.DB, redisClient ...*redis.Client) *Repository {