Merge branch 'main' into test

# Conflicts:
#	backend/cmd/server/VERSION
#	backend/ent/migrate/schema.go
#	backend/ent/mutation.go
#	backend/ent/runtime/runtime.go
#	backend/ent/usagelog.go
#	backend/ent/usagelog/usagelog.go
#	backend/ent/usagelog/where.go
#	backend/ent/usagelog_create.go
#	backend/ent/usagelog_update.go
#	backend/internal/repository/usage_log_repo.go
#	backend/internal/server/api_contract_test.go
#	backend/internal/server/middleware/cors.go
#	backend/internal/service/gateway_service.go

backend/ent/schema/usage_log.go

@@ -124,6 +124,10 @@ func (UsageLog) Fields() []ent.Field {
 			Optional().
 			Nillable(),
 
+		// Cache TTL Override 标记（管理员强制替换了缓存 TTL 计费）
+		field.Bool("cache_ttl_overridden").
+			Default(false),
+
 		// 时间戳（只有 created_at，日志不可修改）
 		field.Time("created_at").
 			Default(time.Now).