fix: add typescript as explicit devDependency and auto-install frontend deps in setup (#70)

frontend/package.json

@@ -14,6 +14,7 @@
   "devDependencies": {
     "stylelint-config-standard": "^40.0.0",
     "ts-lit-plugin": "^2.0.2",
+    "typescript": "^5.9.3",
     "typescript-lit-html-plugin": "^0.9.0",
     "vite": "^7.0.0",
     "vite-plugin-static-copy": "^3.0.0"