fix(desktop): request Badge authorization so the macOS dock badge renders

[muguira]

Problem

On macOS, the desktop app's dock badge (unread count / dot) never renders, and the "Badge app icon" toggle is missing from the app's entry in System Settings → Notifications, so users can't enable it manually either.

The app is setting the badge — setBadgeCount / setBadgeLabel run and the value even registers in LaunchServices (visible via lsappinfo info -only StatusLabel) — but the Dock never paints it.

Root cause

macos_notifications.rs requests notification authorization with only Alert | Sound:

Once an app registers with UNUserNotificationCenter, macOS scopes its notification capabilities to exactly the options granted. If Badge wasn't part of the request, the system suppresses the dock badge entirely — even badges set through the separate NSDockTile API — and hides the "Badge app icon" toggle in System Settings, so there's no user-side workaround.

Fix

Add UNAuthorizationOptions::Badge to the authorization request. One line, plus a comment so it doesn't get dropped later (the connection between this request and the dock tile badge is non-obvious).

Verification

• Built two identical minimal macOS apps that set NSApp.dockTile.badgeLabel and request UN authorization — one with Alert | Sound (matching Buzz today), one with Alert | Sound | Badge. The first never renders a badge and its granted-options bitmask in notification prefs is 6; the second renders the red badge and shows 7 (Badge+Sound+Alert), matching apps like Slack/Chrome/Zoom where badges work.
• With this change, existing installs pick up the wider grant on next launch without re-prompting the user (the request is a superset; macOS extends the grant silently).
• Full CI run on this change (fork): Desktop Build macOS, Desktop Core, Desktop E2E Relay, 4× Desktop Smoke E2E, 2× Desktop E2E Integration, Rust Lint, Windows Rust — all green.

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