feat(channel): improve cache strategy and add restriction logging

- Change channel cache TTL from 60s to 10min (reduce unnecessary DB queries)
- Actively rebuild cache after CRUD instead of lazy invalidation
- Add slog.Warn logging for channel pricing restriction blocks (4 places)

backend/internal/service/channel_service.go

@@ -133,8 +133,8 @@ func (r ChannelMappingResult) ToUsageFields(reqModel, upstreamModel string) Chan
 }
 
 const (
-	channelCacheTTL       = 60 * time.Second
-	channelErrorTTL       = 5 * time.Second // DB 错误时的短缓存
+	channelCacheTTL       = 10 * time.Minute
+	channelErrorTTL       = 5 * time.Second  // DB 错误时的短缓存
 	channelCacheDBTimeout = 10 * time.Second
 )
 
@@ -333,6 +333,11 @@ func matchingPlatforms(groupPlatform string) []string {
 func (s *ChannelService) invalidateCache() {
 	s.cache.Store((*channelCache)(nil))
 	s.cacheSF.Forget("channel_cache")
+
+	// 主动重建缓存，确保 CRUD 后立即生效
+	if _, err := s.buildCache(context.Background()); err != nil {
+		slog.Warn("failed to rebuild channel cache after invalidation", "error", err)
+	}
 }
 
 // matchWildcard 在通配符定价中查找匹配项（最先匹配到优先）

backend/internal/service/gateway_service.go

@@ -1199,6 +1199,9 @@ func (s *GatewayService) SelectAccountForModelWithExclusions(ctx context.Context
 	// Claude Code 限制可能已将 groupID 解析为 fallback group，
 	// 渠道限制预检查必须使用解析后的分组。
 	if s.checkChannelPricingRestriction(ctx, groupID, requestedModel) {
+		slog.Warn("channel pricing restriction blocked request",
+			"group_id", derefGroupID(groupID),
+			"model", requestedModel)
 		return nil, fmt.Errorf("%w supporting model: %s (channel pricing restriction)", ErrNoAvailableAccounts, requestedModel)
 	}
 
@@ -1241,6 +1244,9 @@ func (s *GatewayService) SelectAccountWithLoadAwareness(ctx context.Context, gro
 	// Claude Code 限制可能已将 groupID 解析为 fallback group，
 	// 渠道限制预检查必须使用解析后的分组。
 	if s.checkChannelPricingRestriction(ctx, groupID, requestedModel) {
+		slog.Warn("channel pricing restriction blocked request",
+			"group_id", derefGroupID(groupID),
+			"model", requestedModel)
 		return nil, fmt.Errorf("%w supporting model: %s (channel pricing restriction)", ErrNoAvailableAccounts, requestedModel)
 	}
 

backend/internal/service/openai_gateway_service.go

@@ -1202,6 +1202,9 @@ func (s *OpenAIGatewayService) SelectAccountForModelWithExclusions(ctx context.C
 
 func (s *OpenAIGatewayService) selectAccountForModelWithExclusions(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}, stickyAccountID int64) (*Account, error) {
 	if s.checkChannelPricingRestriction(ctx, groupID, requestedModel) {
+		slog.Warn("channel pricing restriction blocked request",
+			"group_id", derefGroupID(groupID),
+			"model", requestedModel)
 		return nil, fmt.Errorf("%w supporting model: %s (channel pricing restriction)", ErrNoAvailableAccounts, requestedModel)
 	}
 
@@ -1379,6 +1382,9 @@ func (s *OpenAIGatewayService) isBetterAccount(candidate, current *Account) bool
 // SelectAccountWithLoadAwareness selects an account with load-awareness and wait plan.
 func (s *OpenAIGatewayService) SelectAccountWithLoadAwareness(ctx context.Context, groupID *int64, sessionHash string, requestedModel string, excludedIDs map[int64]struct{}) (*AccountSelectionResult, error) {
 	if s.checkChannelPricingRestriction(ctx, groupID, requestedModel) {
+		slog.Warn("channel pricing restriction blocked request",
+			"group_id", derefGroupID(groupID),
+			"model", requestedModel)
 		return nil, fmt.Errorf("%w supporting model: %s (channel pricing restriction)", ErrNoAvailableAccounts, requestedModel)
 	}