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).

test/desktop/prefs.test.ts

@@ -18,6 +18,8 @@ const EXPECTED_DEFAULTS: DesktopPrefs = {
   openAtLogin: false,
   notifyOnApproval: true,
   notifyOnStatusChange: true,
+  remoteHosts: [],
+  selectedHostId: null,
 }
 
 describe('defaultPrefs', () => {
@@ -60,6 +62,8 @@ describe('validatePrefs', () => {
       openAtLogin: true,
       notifyOnApproval: false,
       notifyOnStatusChange: false,
+      remoteHosts: [],
+      selectedHostId: null,
     }
 
     // Act