refactor backend packages and global db service

backend/internal/models/task_share.go

@@ -0,0 +1,15 @@
+package models
+
+import "time"
+
+type SenlinAgentTaskShare struct {
+	ID         uint   `gorm:"primaryKey"`
+	TaskID     uint   `gorm:"index;not null"`
+	ObjectType string `gorm:"not null"`
+	ObjectID   uint   `gorm:"not null"`
+	CreatedAt  time.Time
+}
+
+func (SenlinAgentTaskShare) TableName() string {
+	return "senlin_agent_task_shares"
+}