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/playwright.config.js

@@ -0,0 +1,17 @@
+import { defineConfig, devices } from '@playwright/test';
+
+// Playwright config for M1 end-to-end tests.
+// base URL points at the LAN UAT container (card M1-6). Override with BASE_URL.
+export default defineConfig({
+	testDir: './tests/e2e',
+	timeout: 60_000,
+	use: {
+		baseURL: process.env.BASE_URL || 'http://192.168.1.202:18080'
+	},
+	projects: [
+		{
+			name: 'chromium',
+			use: { ...devices['Desktop Chrome'] }
+		}
+	]
+});