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

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+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);
+});

frontend/tests/unit/smoke.test.js

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+import { describe, it, expect } from 'vitest';
+
+// Smoke test for the M1-1 harness: proves the JS unit runner works end-to-end.
+// This is deliberately trivial — later cards (M1-2+) replace it with the
+// deterministic-core suite. It must pass to certify the harness is GREEN.
+describe('M1 harness smoke', () => {
+	it('adds numbers (harness is live)', () => {
+		expect(1 + 1).toBe(2);
+	});
+});