v0.2.1 — watchdog false positive fix

Fixed

• BLE watchdog no longer trips on hash-neutral hook events. v0.2.0's watchdog watched `last_hook_event_at` vs `last_gif_sent_at`, but `last_hook_event_at` was bumped for every webhook event — including events that don't affect display state (e.g. `Notification`, which falls through `event::handle_event`'s match to `_ => {}`). The BLE render loop correctly stayed in the heartbeat branch waiting for its 30s tick, and the watchdog mistook that for a stuck loop and forced a spurious reconnect.

  The fix: in the loop's hash-unchanged `else` branch, bump `last_gif_sent_at` to now. Semantically that field is now "last point in time the loop is known to be caught up", which is true whenever the rendered hash matches what's on the device. Genuine wedges still never reach that branch, so the original v0.2.0 protection is preserved.