chore(toolkit): bump for lock-screen artwork off-main crash fix (e672637)

Bumps ios-audiobooktoolkit to the fix for the MPMediaItemArtwork request-handler
block-destroy crash — the toolkit's updateLockScreenCoverArtwork built a
non-@sendable artwork handler capturing the UIImage, which MediaPlayer destroys
on its own background queue → block_destroy_helper EXC_BREAKPOINT (Crashlytics
e672637, seen on Palace 3.2.0 audiobook opens).

The toolkit fix (ThePalaceProject/ios-audiobooktoolkit#198) mirrors the app-side
NowPlayingCoordinator fix (#1218) that resolved the identical crash on the app's
own now-playing artwork path.

This is the develop-visible landing of that fix (the toolkit is a submodule).
Companion crash 4a92d371 (app-side updateNowPlayingInfo) is ALREADY fixed on
develop by #1218 — this bump closes the remaining toolkit half.

**Gated on #198 merging:** the submodule currently points at the fix branch;
the SHA finalizes to the merged toolkit main commit once #198 lands. Opened now
so ios-core CI build-verifies the integration (the toolkit repo has no CI and
isn't built in the worktree).

**Not done:** re-point submodule to the merged #198 main SHA after it lands.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: t