Add container restart/stop/start controls

- Add HandleAppRestart, HandleAppStop, HandleAppStart handlers
- Wire up POST routes for /apps/{id}/restart, /stop, /start
- Use helper function to reduce code duplication

internal/server/routes.go

@@ -64,6 +64,9 @@ func (s *Server) SetupRoutes() {
 		r.Post("/apps/{id}/deploy", s.handlers.HandleAppDeploy())
 		r.Get("/apps/{id}/deployments", s.handlers.HandleAppDeployments())
 		r.Get("/apps/{id}/logs", s.handlers.HandleAppLogs())
+		r.Post("/apps/{id}/restart", s.handlers.HandleAppRestart())
+		r.Post("/apps/{id}/stop", s.handlers.HandleAppStop())
+		r.Post("/apps/{id}/start", s.handlers.HandleAppStart())
 
 		// Environment variables
 		r.Post("/apps/{id}/env-vars", s.handlers.HandleEnvVarAdd())