feat(m1-1): scaffold SvelteKit + Dockerfile + TDD test harness

- SvelteKit (JS, adapter-node) home page + /api/health route
- frontend/Dockerfile multi-stage build->serve (slabuploader-m1:local, 349MB)
- Test harness: Vitest unit + Playwright e2e; smoke tests RED->GREEN verified
- Build, image build, and image serve all verified

frontend/tests/e2e/smoke.spec.js

@@ -0,0 +1,12 @@
+import { test, expect } from '@playwright/test';
+
+// E2E smoke: the app serves and the health route responds.
+// Later cards extend this to walk the full 5-state capture flow.
+test('M1-1 harness smoke: app serves + health ok', async ({ page, request }) => {
+	await page.goto('/');
+	await expect(page).toHaveTitle(/SlabUploader/);
+	const res = await request.get('/api/health');
+	expect(res.ok()).toBeTruthy();
+	const body = await res.json();
+	expect(body.ok).toBe(true);
+});