fix: prevent slider snapping back after seek

[Mestane]

Problem

When seeking via the progress slider, the slider briefly snaps back to the previous position before settling at the correct seek point. This is more pronounced on lower-end hardware where the MPRIS position update takes longer to come through.

Fix

Added an isSeeking property to the slider and a 500ms cooldown Timer (consistent with the approach already used in LyricsService.qml). The Binding is now suspended while isSeeking is true, giving Quickshell enough time to receive and reflect the updated MPRIS position before the binding re-activates.

fixed #1485

[soramanew]

Is this still an issue in v2?

[Mestane]

Is this still an issue in v2?

In v2, the media slider appears to be drag-only clicking directly to a position doesn't seem to work, so the snap-back issue no longer occurs in practice. However, if click-to-seek is intended behavior in v2, this fix would need to be reworked since the current implementation is not compatible with v2's slider changes.

[Mestane]

Is this still an issue in v2?

Fixed in v2 the root cause was in StyledSlider.qml; onReleased was emitting the original position instead of the clicked one since dragMovement is never updated on a bare click. See #1539