feat(scheduler): 引入调度快照缓存与 outbox 回放

- 调度热路径优先读 Redis 快照，保留分组排序语义
- outbox 回放 + 全量重建纠偏，失败重试不推进水位
- 自动 Atlas 基线对齐并同步调度配置示例

backend/internal/service/gateway_service.go

@@ -151,6 +151,7 @@ type GatewayService struct {
 	userSubRepo         UserSubscriptionRepository
 	cache               GatewayCache
 	cfg                 *config.Config
+	schedulerSnapshot   *SchedulerSnapshotService
 	billingService      *BillingService
 	rateLimitService    *RateLimitService
 	billingCacheService *BillingCacheService
@@ -169,6 +170,7 @@ func NewGatewayService(
 	userSubRepo UserSubscriptionRepository,
 	cache GatewayCache,
 	cfg *config.Config,
+	schedulerSnapshot *SchedulerSnapshotService,
 	concurrencyService *ConcurrencyService,
 	billingService *BillingService,
 	rateLimitService *RateLimitService,
@@ -185,6 +187,7 @@ func NewGatewayService(
 		userSubRepo:         userSubRepo,
 		cache:               cache,
 		cfg:                 cfg,
+		schedulerSnapshot:   schedulerSnapshot,
 		concurrencyService:  concurrencyService,
 		billingService:      billingService,
 		rateLimitService:    rateLimitService,
@@ -745,6 +748,9 @@ func (s *GatewayService) resolvePlatform(ctx context.Context, groupID *int64, gr
 }
 
 func (s *GatewayService) listSchedulableAccounts(ctx context.Context, groupID *int64, platform string, hasForcePlatform bool) ([]Account, bool, error) {
+	if s.schedulerSnapshot != nil {
+		return s.schedulerSnapshot.ListSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
+	}
 	useMixed := (platform == PlatformAnthropic || platform == PlatformGemini) && !hasForcePlatform
 	if useMixed {
 		platforms := []string{platform, PlatformAntigravity}
@@ -821,6 +827,13 @@ func (s *GatewayService) tryAcquireAccountSlot(ctx context.Context, accountID in
 	return s.concurrencyService.AcquireAccountSlot(ctx, accountID, maxConcurrency)
 }
 
+func (s *GatewayService) getSchedulableAccount(ctx context.Context, accountID int64) (*Account, error) {
+	if s.schedulerSnapshot != nil {
+		return s.schedulerSnapshot.GetAccount(ctx, accountID)
+	}
+	return s.accountRepo.GetByID(ctx, accountID)
+}
+
 func sortAccountsByPriorityAndLastUsed(accounts []*Account, preferOAuth bool) {
 	sort.SliceStable(accounts, func(i, j int) bool {
 		a, b := accounts[i], accounts[j]
@@ -851,7 +864,7 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 		if err == nil && accountID > 0 {
 			if _, excluded := excludedIDs[accountID]; !excluded {
-				account, err := s.accountRepo.GetByID(ctx, accountID)
+				account, err := s.getSchedulableAccount(ctx, accountID)
 				// 检查账号分组归属和平台匹配（确保粘性会话不会跨分组或跨平台）
 				if err == nil && s.isAccountInGroup(account, groupID) && account.Platform == platform && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
 					if err := s.cache.RefreshSessionTTL(ctx, derefGroupID(groupID), sessionHash, stickySessionTTL); err != nil {
@@ -864,16 +877,11 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 	}
 
 	// 2. 获取可调度账号列表（单平台）
-	var accounts []Account
-	var err error
-	if s.cfg.RunMode == config.RunModeSimple {
-		// 简易模式：忽略 groupID，查询所有可用账号
-		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
-	} else if groupID != nil {
-		accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatform(ctx, *groupID, platform)
-	} else {
-		accounts, err = s.accountRepo.ListSchedulableByPlatform(ctx, platform)
+	forcePlatform, hasForcePlatform := ctx.Value(ctxkey.ForcePlatform).(string)
+	if hasForcePlatform && forcePlatform == "" {
+		hasForcePlatform = false
 	}
+	accounts, _, err := s.listSchedulableAccounts(ctx, groupID, platform, hasForcePlatform)
 	if err != nil {
 		return nil, fmt.Errorf("query accounts failed: %w", err)
 	}
@@ -935,7 +943,6 @@ func (s *GatewayService) selectAccountForModelWithPlatform(ctx context.Context,
 // selectAccountWithMixedScheduling 选择账户（支持混合调度）
 // 查询原生平台账户 + 启用 mixed_scheduling 的 antigravity 账户
 func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, nativePlatform string) (*Account, error) {
-	platforms := []string{nativePlatform, PlatformAntigravity}
 	preferOAuth := nativePlatform == PlatformGemini
 
 	// 1. 查询粘性会话
@@ -943,7 +950,7 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 		accountID, err := s.cache.GetSessionAccountID(ctx, derefGroupID(groupID), sessionHash)
 		if err == nil && accountID > 0 {
 			if _, excluded := excludedIDs[accountID]; !excluded {
-				account, err := s.accountRepo.GetByID(ctx, accountID)
+				account, err := s.getSchedulableAccount(ctx, accountID)
 				// 检查账号分组归属和有效性：原生平台直接匹配，antigravity 需要启用混合调度
 				if err == nil && s.isAccountInGroup(account, groupID) && account.IsSchedulableForModel(requestedModel) && (requestedModel == "" || s.isModelSupportedByAccount(account, requestedModel)) {
 					if account.Platform == nativePlatform || (account.Platform == PlatformAntigravity && account.IsMixedSchedulingEnabled()) {
@@ -958,13 +965,7 @@ func (s *GatewayService) selectAccountWithMixedScheduling(ctx context.Context, g
 	}
 
 	// 2. 获取可调度账号列表
-	var accounts []Account
-	var err error
-	if groupID != nil {
-		accounts, err = s.accountRepo.ListSchedulableByGroupIDAndPlatforms(ctx, *groupID, platforms)
-	} else {
-		accounts, err = s.accountRepo.ListSchedulableByPlatforms(ctx, platforms)
-	}
+	accounts, _, err := s.listSchedulableAccounts(ctx, groupID, nativePlatform, false)
 	if err != nil {
 		return nil, fmt.Errorf("query accounts failed: %w", err)
 	}