fix: harden controlled AI session consistency

backend/internal/models/ai_rate_bucket.go

@@ -0,0 +1,19 @@
+package models
+
+import "time"
+
+// SenlinAgentAIRateBucket 保存用户在固定窗口内已占用的 AI 请求配额。
+// 复合唯一键让单条 UPSERT 在数据库层完成跨进程并发仲裁。
+type SenlinAgentAIRateBucket struct {
+	ID          uint      `gorm:"primaryKey"`
+	UserID      uint      `gorm:"not null;uniqueIndex:uidx_senlin_agent_ai_rate_bucket,priority:1"`
+	Action      string    `gorm:"size:100;not null;uniqueIndex:uidx_senlin_agent_ai_rate_bucket,priority:2"`
+	WindowStart time.Time `gorm:"not null;uniqueIndex:uidx_senlin_agent_ai_rate_bucket,priority:3"`
+	Count       int       `gorm:"not null"`
+	CreatedAt   time.Time
+	UpdatedAt   time.Time
+}
+
+func (SenlinAgentAIRateBucket) TableName() string {
+	return "senlin_agent_ai_rate_buckets"
+}

backend/internal/models/new.go

@@ -38,6 +38,7 @@ func AutoMigrate(database *gorm.DB) error {
 		&SenlinAgentProjectEvent{},
 		&SenlinAgentAIKey{},
 		&SenlinAgentAICallLog{},
+		&SenlinAgentAIRateBucket{},
 		&SenlinAgentTaskShare{},
 	)
 }