gui: live Input Monitoring + Bluetooth permission status via a polling watcher

[AprilNEA]

Problem

The Settings → Permissions section queries Input Monitoring (IOHIDCheckAccess) and Bluetooth (CBManager.authorization) via FFI at render time, inside permissions_group. Two issues:

1. Per-repaint cost: the FFI runs on every Settings render (each switch toggle, language change, appearance change), not just on open.
2. Stale status: nothing re-renders Settings when IM/Bluetooth status changes, so a grant-and-return doesn't update the row until an unrelated repaint. Only Accessibility is live, because its dedicated watcher calls refresh_windows() on change.

The three rows sit in one group at inconsistent altitude (one watcher-pushed, two pull-on-render with no driver).

Proposal

Generalize the existing accessibility watcher (watchers/accessibility.rs) into a permissions watcher that, on each tick (~1.2 s), checks all three permissions and refresh_windows() on any change. Store all three in AppState (alongside accessibility_granted); settings.rs reads the cached fields instead of calling FFI per render.

Acceptance

• Granting Input Monitoring / Bluetooth in System Settings updates the Settings row within ~1–2 s without any other interaction.
• No permission FFI on the Settings render hot path.

Context: review of #45 (findings #8, #9). Pairs with the broader "permissions UX" work.

[linear-code]

OLG-23