fix: prevent error flash on project delete by using SPA navigation and blocking re-fetch

web/src/routes/projects/[id]/+page.svelte

@@ -1,5 +1,6 @@
 <script lang="ts">
 	import { page } from '$app/stores';
+	import { goto } from '$app/navigation';
 	import type { Project, Stage, Instance, Deploy } from '$lib/types';
 	import * as api from '$lib/api';
 	import StatusBadge from '$lib/components/StatusBadge.svelte';
@@ -243,19 +244,23 @@
 		}
 	}
 
+	let deleted = $state(false);
+
 	async function handleDeleteProject() {
 		showDeleteConfirm = false;
+		deleted = true;
 		try {
 			await api.deleteProject(projectId);
-			window.location.href = '/projects';
+			goto('/projects');
 		} catch (e) {
+			deleted = false;
 			error = e instanceof Error ? e.message : $t('projectDetail.deleteFailed');
 		}
 	}
 
 	$effect(() => {
 		void projectId;
-		loadProject();
+		if (!deleted) loadProject();
 	});
 </script>