scaffold: modern rewrite skeleton (backend + frontend PWA) + roadmap

modern/frontend/sw.js

@@ -0,0 +1,12 @@
+// Minimal service worker (cache-first for shell)
+const CACHE = 'liferpg-shell-v1'
+self.addEventListener('install', (e) => {
+  e.waitUntil(
+    caches.open(CACHE).then((cache) => cache.addAll(['/','/index.html']))
+  )
+})
+self.addEventListener('fetch', (e) => {
+  e.respondWith(
+    caches.match(e.request).then((r) => r || fetch(e.request))
+  )
+})