Drop cookie import; click-through notifications; per-app zoom

The cookie import is gone. It worked mechanically - 43 cookies decrypted
from Arc and verifiably visible to the page - but Google, Microsoft and
Odoo all refused the imported sessions, because each binds a session to
the browser that created it. Signing in once inside the app is simpler
and actually works, so the whole path is deleted rather than kept as a
feature that mostly fails. That takes rusqlite, aes, cbc, pbkdf2, hmac,
sha1 and sha2 out of the build with it.

Notifications are now raised through mac-notification-sys rather than
Tauri's notification plugin, because the plugin cannot report that one
was clicked. A click switches to the app that raised it and then runs
the page's own click handler - the only thing that knows which message
the notification was about.

Zoom is per app, on a fixed ladder so Cmd+0 returns to exactly 100%.
The shortcuts are menu-bar accelerators rather than a key listener,
since the keystroke has to work while a remote page has focus.

The hidden-element count is off the nav rows.

src/components/Nav.tsx

@@ -137,14 +137,6 @@ export default function Nav({
       >
         <Favicon url={app.url} name={app.name} />
         <span className="truncate">{app.name}</span>
-        {app.hidden.length > 0 && (
-          <span
-            title={`${app.hidden.length} element${app.hidden.length === 1 ? "" : "s"} hidden here`}
-            className="ml-auto font-mono text-[10px] opacity-50"
-          >
-            {app.hidden.length}
-          </span>
-        )}
       </button>
     </li>
   );