test: fix pre-existing failures — localStorage polyfill + prefs shape drift

- jsdom 29's localStorage methods are undefined under this vitest config, so
  every frontend test calling localStorage.clear()/setItem() threw. Add a
  shared in-memory Web Storage polyfill via setupFiles (no-op when a working
  Storage exists / in node env). Fixes quick-reply, push, projects-panel (135 tests).
- Update desktop prefs test: defaultPrefs gained remoteHosts/selectedHostId
  (remote-host mTLS work); sync EXPECTED_DEFAULTS and the round-trip fixture.

Full suite now green: 1473 passed (was 142 failing).

vitest.config.ts

@@ -4,6 +4,10 @@ export default defineConfig({
   test: {
     include: ['test/**/*.test.ts'],
     environment: 'node',
+    // jsdom 29's localStorage methods are undefined under this config; a shared
+    // in-memory Web Storage polyfill fixes the frontend (@vitest-environment
+    // jsdom) tests that call localStorage.clear()/setItem(). No-op in node env.
+    setupFiles: ['test/setup/local-storage.ts'],
     // Scaffold has no tests yet; don't fail the script until modules add theirs.
     passWithNoTests: true,
     // Coverage target is the global 80% rule; enforced with `--coverage`.