v1.2.8

Handle backward seeks and blank-cutoff sync

Add .lscache entry to .gitignore and improve lyric timing logic to detect backward seeks. Introduces previousEffectiveTime and didSeekBackward (0.75s threshold) to stabilize effectiveTime handling, and updates blank-cutoff logic to allow lowering latchedBlankCutoffIndex when seeking backward; retains existing behavior for forward progression. Also cleans up related variable usage for clarity.