fix(api): enforce project identifier uniqueness

backend/internal/models/new.go

@@ -8,7 +8,8 @@ import (
 var DBService *gorm.DB
 
 func New(dsn string) error {
-	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{})
+	// 启用 Gorm 跨驱动错误翻译，业务层无需解析 Postgres 错误文本或 SQLSTATE。
+	db, err := gorm.Open(postgres.Open(dsn), &gorm.Config{TranslateError: true})
 	if err != nil {
 		return err
 	}

backend/internal/models/project.go

@@ -5,10 +5,10 @@ import "time"
 type SenlinAgentProject struct {
 	ID            uint   `gorm:"primaryKey"`
 	Identity      string `gorm:"type:char(36);uniqueIndex"`
-	OwnerID       uint   `gorm:"index;not null"`
+	OwnerID       uint   `gorm:"index;not null;uniqueIndex:uidx_senlin_agent_projects_owner_identifier,priority:1"`
 	OwnerIdentity string `gorm:"type:char(36);index"`
 	Name          string `gorm:"not null"`
-	Identifier    string `gorm:"index"`
+	Identifier    string `gorm:"index;uniqueIndex:uidx_senlin_agent_projects_owner_identifier,priority:2"`
 	Icon          string
 	Background    string
 	Description   string