refactor: shorten model and table prefixes

backend/internal/models/ai_key.go

@@ -2,7 +2,7 @@ package models
 
 import "time"
 
-type SenlinAgentAIKey struct {
+type SaAIKey struct {
 	ID              uint   `gorm:"primaryKey"`
 	Identity        string `gorm:"type:char(36);uniqueIndex"`
 	UserID          uint   `gorm:"uniqueIndex;not null"`
@@ -13,6 +13,6 @@ type SenlinAgentAIKey struct {
 	UpdatedAt       time.Time
 }
 
-func (SenlinAgentAIKey) TableName() string {
-	return "senlin_agent_ai_keys"
+func (SaAIKey) TableName() string {
+	return "sa_ai_keys"
 }