Dispose manual ping cooldown timer

[robekl]

Problem

The manual ping cooldown timer was created and used for periodic UI updates, but it was not disposed when app state was torn down. That leaves a live timer behind after provider disposal, which is a lifecycle leak and can cause unnecessary work after teardown.

Change

Added explicit disposal for the manual ping cooldown timer during app-state cleanup.

Why This Fixes It

The timer now follows the same ownership and teardown path as the other countdown timers. That removes the leaked periodic callback and ensures no timer-driven updates survive provider disposal.

[MrAlders0n]

Nice catch! Before I merge this, could you also add _manualPingCooldownTimer.stop() to the disconnect/cleanup paths where the other timers are already stopped? Right now it's missing from:

1. User disconnect
2. BLE disconnect handler
3. Reconnect cleanup
4. Auto-ping stop

The 15s self-stop makes it low-risk, but since you're already fixing this timer's lifecycle it'd be good to make it complete in one PR. Let me know if you have time to add that!

[robekl]

Let me know if you have time to add that!

Done!

[446564]

can you pull and run dart format then commit the formatting changes?