Precache hashed bundles and revision the PWA service worker

- Add a build-only Vite plugin (admin/vite-sw-plugin.ts) that, after the
  bundle is written, injects every same-origin script/link asset referenced
  by dist/index.html into dist/sw.js's precache, so the offline shell renders
  immediately after install (PWA-001).
- Replace the literal cache version with a build revision (sha256 of the built
  index.html and sw.js source, truncated) used in both cache names, so each
  release installs a new worker with fresh caches (PWA-002).
- On activate, delete only stale nestquest-admin-* caches; unrelated
  same-origin caches survive (PWA-003).
- Add Vitest regressions for all three findings.

Task: 96ab3c0b-7554-4098-8af1-2be7815f8929

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

admin/vite.config.ts

@@ -1,9 +1,10 @@
 import { defineConfig } from "vitest/config";
 import react from "@vitejs/plugin-react";
+import { serviceWorkerInjectPlugin } from "./vite-sw-plugin";
 
 export default defineConfig({
-  plugins: [react()],
+  plugins: [react(), serviceWorkerInjectPlugin()],
   test: {
     environment: "jsdom",
   },
-});
+});