修复：审查发现的高优先问题（竞态/初始化/碰撞）

- app.go: profileSvc移入App struct，用a.mu保护
- sqlite.go: InitFast加sync.Once防并发双重初始化
- client.go: Manager.Connect加sync.Mutex防竞态泄漏SSH
- service.go: 临时文件用os.CreateTemp防时间戳碰撞
- connection-manager: 密码缺失时不再塞入假WailsTransport

app.go

@@ -38,6 +38,7 @@ type App struct {
 	pdfAPI        *api.PdfAPI
 	filesystem    *filesystem.FileSystemService
 	sftpService   *sftp.Service
+	profileSvc    *service.ProfileService
 	isAlwaysOnTop bool
 	mu            sync.Mutex
 }
@@ -986,13 +987,13 @@ type SaveProfileRequest struct {
 	LastConnected *int64     `json:"last_connected"`
 }
 
-var profileSvc *service.ProfileService
-
 func (a *App) ensureProfileSvc() *service.ProfileService {
-	if profileSvc == nil {
-		profileSvc = service.NewProfileService()
+	a.mu.Lock()
+	defer a.mu.Unlock()
+	if a.profileSvc == nil {
+		a.profileSvc = service.NewProfileService()
 	}
-	return profileSvc
+	return a.profileSvc
 }
 
 func (a *App) LoadConnectionProfiles() ([]map[string]interface{}, error) {