fix(desktop): notification click no longer reloads to a dead page (0.1.9/batch62)

Root cause of the persistent "notification opens a dead page / no Join" bug:
openFromNotif gated the in-place open on `window.ME`, but ME is declared with
`let` — which never creates a global property — so window.ME was ALWAYS
undefined and every click hit the full-page-reload fallback. Use bare `ME`.

Also:
- Notifications fire instantly: never block on the DP download. Use the photo
  only if already cached; warm the cache in the background + pre-warm all
  contact DPs on chat load (precache-avatars IPC). Removes the ~2.5s lag.
- Wire call Join/Decline handlers BEFORE firing the OS notification so Join is
  live the instant the invite popup appears (was dead until the toast settled).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

desktop/preload.js

@@ -22,6 +22,9 @@ contextBridge.exposeInMainWorld('bizConnectNative', Object.freeze({
   // Native Windows toast with an inline reply box. Resolves to {text} (replied), {open} (clicked)
   // or null. Lets the user reply to a chat straight from the notification.
   replyNotify: (payload) => ipcRenderer.invoke('reply-notification', payload),
+  // Pre-warm the notification DP cache with contact photo URLs (called after chats load) so the first
+  // toast from anyone already has their photo — no per-notification download lag.
+  precacheAvatars: (urls) => { try { return ipcRenderer.invoke('precache-avatars', urls); } catch (_) { return Promise.resolve(false); } },
   // Manual "Check for updates" from Settings. Resolves {status:'available'|'current'|'dev'|'error', version?}.
   // On 'available' the shell downloads in the background and prompts to restart when ready.
   checkForUpdates: () => ipcRenderer.invoke('check-updates'),