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/package.json

@@ -0,0 +1,28 @@
+{
+  "name": "slab-uploader-frontend",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "scripts": {
+    "dev": "vite dev",
+    "build": "vite build",
+    "preview": "vite preview",
+    "check": "svelte-kit sync && svelte-check --tsconfig ./tsconfig.json",
+    "test:unit": "vitest run",
+    "test:e2e": "playwright test"
+  },
+  "devDependencies": {
+    "@playwright/test": "^1.63.0",
+    "@sveltejs/adapter-node": "^5.2.0",
+    "@sveltejs/kit": "^2.21.0",
+    "@sveltejs/vite-plugin-svelte": "^5.0.0",
+    "svelte": "^5.0.0",
+    "svelte-check": "^4.1.0",
+    "typescript": "^5.8.0",
+    "vite": "^6.3.0",
+    "vitest": "^3.0.0"
+  },
+  "dependencies": {
+    "idb-keyval": "^6.2.1"
+  }
+}