fix: 修复 golangci-lint depguard 和 gofmt 错误

将 redis leader lock 逻辑从 service 层抽取为 LeaderLocker 接口，
实现移至 repository 层，消除 service 层对 redis 的直接依赖。

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

backend/internal/repository/scheduled_test_repo.go

@@ -3,9 +3,14 @@ package repository
 import (
 	"context"
 	"database/sql"
+	"hash/fnv"
+	"sync"
 	"time"
 
+	"github.com/Wei-Shaw/sub2api/internal/pkg/logger"
 	"github.com/Wei-Shaw/sub2api/internal/service"
+	"github.com/google/uuid"
+	"github.com/redis/go-redis/v9"
 )
 
 // --- Plan Repository ---
@@ -181,3 +186,83 @@ func scanPlans(rows *sql.Rows) ([]*service.ScheduledTestPlan, error) {
 	}
 	return plans, rows.Err()
 }
+
+// --- LeaderLocker ---
+
+var redisReleaseScript = redis.NewScript(`
+if redis.call("GET", KEYS[1]) == ARGV[1] then
+  return redis.call("DEL", KEYS[1])
+end
+return 0
+`)
+
+type leaderLocker struct {
+	db              *sql.DB
+	redisClient     *redis.Client
+	instanceID      string
+	warnNoRedisOnce sync.Once
+}
+
+// NewLeaderLocker creates a LeaderLocker that tries Redis first, then falls back to pg advisory lock.
+func NewLeaderLocker(db *sql.DB, redisClient *redis.Client) service.LeaderLocker {
+	return &leaderLocker{
+		db:          db,
+		redisClient: redisClient,
+		instanceID:  uuid.NewString(),
+	}
+}
+
+func (l *leaderLocker) TryAcquire(ctx context.Context, key string, ttl time.Duration) (func(), bool) {
+	if l.redisClient != nil {
+		ok, err := l.redisClient.SetNX(ctx, key, l.instanceID, ttl).Result()
+		if err == nil {
+			if !ok {
+				return nil, false
+			}
+			return func() {
+				_, _ = redisReleaseScript.Run(ctx, l.redisClient, []string{key}, l.instanceID).Result()
+			}, true
+		}
+		l.warnNoRedisOnce.Do(func() {
+			logger.LegacyPrintf("repository.leader_locker", "[LeaderLocker] Redis SetNX failed; falling back to DB advisory lock: %v", err)
+		})
+	} else {
+		l.warnNoRedisOnce.Do(func() {
+			logger.LegacyPrintf("repository.leader_locker", "[LeaderLocker] Redis not configured; using DB advisory lock")
+		})
+	}
+
+	// Fallback: pg_try_advisory_lock
+	return tryAdvisoryLock(ctx, l.db, hashLockID(key))
+}
+
+func tryAdvisoryLock(ctx context.Context, db *sql.DB, lockID int64) (func(), bool) {
+	if db == nil {
+		return nil, false
+	}
+	conn, err := db.Conn(ctx)
+	if err != nil {
+		return nil, false
+	}
+	acquired := false
+	if err := conn.QueryRowContext(ctx, "SELECT pg_try_advisory_lock($1)", lockID).Scan(&acquired); err != nil {
+		_ = conn.Close()
+		return nil, false
+	}
+	if !acquired {
+		_ = conn.Close()
+		return nil, false
+	}
+	return func() {
+		unlockCtx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+		defer cancel()
+		_, _ = conn.ExecContext(unlockCtx, "SELECT pg_advisory_unlock($1)", lockID)
+		_ = conn.Close()
+	}, true
+}
+
+func hashLockID(key string) int64 {
+	h := fnv.New64a()
+	_, _ = h.Write([]byte(key))
+	return int64(h.Sum64())
+}

backend/internal/repository/wire.go

@@ -53,9 +53,10 @@ var ProviderSet = wire.NewSet(
 	NewAPIKeyRepository,
 	NewGroupRepository,
 	NewAccountRepository,
-	NewSoraAccountRepository,              // Sora 账号扩展表仓储
-	NewScheduledTestPlanRepository,        // 定时测试计划仓储
-	NewScheduledTestResultRepository,      // 定时测试结果仓储
+	NewSoraAccountRepository,         // Sora 账号扩展表仓储
+	NewScheduledTestPlanRepository,   // 定时测试计划仓储
+	NewScheduledTestResultRepository, // 定时测试结果仓储
+	NewLeaderLocker,                  // 分布式 leader 选举
 	NewProxyRepository,
 	NewRedeemCodeRepository,
 	NewPromoCodeRepository,