refactor backend packages and global db service

backend/internal/models/project_event.go

@@ -0,0 +1,18 @@
+package models
+
+import "time"
+
+type SenlinAgentProjectEvent struct {
+	ID         uint   `gorm:"primaryKey"`
+	ProjectID  uint   `gorm:"index;not null"`
+	ActorID    uint   `gorm:"index;not null"`
+	EventType  string `gorm:"not null"`
+	EntityType string `gorm:"not null"`
+	EntityID   uint   `gorm:"not null"`
+	Summary    string `gorm:"not null"`
+	CreatedAt  time.Time
+}
+
+func (SenlinAgentProjectEvent) TableName() string {
+	return "senlin_agent_project_events"
+}