v1.2.1 — fix a rare garbage cue-countdown value

Bug fix on top of v1.2.0 (independent per-deck panels) — no other changes.

Fixed a rare bug where the "next cue point" countdown could show a nonsensical, huge value (e.g. "8547483333399940578367897600.0s") instead of a real countdown, on some tracks. Root cause: the cue-point decoder's byte-pattern scan could coincidentally match unrelated bytes elsewhere in the track's data on certain tracks, misreading them as a cue time. Now rejects any decoded cue time beyond what any real track could need (6 hours).

See v1.2.0's release notes for what's new since v1.1.0.