🎨 Palette: [UX improvement] Add accessible name and tooltip to audio playback slider

[awest813]

💡 What: Added setToolTipText and getAccessibleContext().setAccessibleName(...) to the JSlider used for audio seeking in SeekableFlacPlayerGui.java.
🎯 Why: Desktop application sliders often lack context for users navigating via keyboard or screen readers. This ensures the slider has an accessible name and a helpful visual tooltip.
♿ Accessibility: Improved screen reader support by providing an explicit accessible name ("Audio Position") and visual tooltip ("Seek Audio Position") for the raw JSlider component.

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PR created automatically by Jules for task 4544108730583203542 started by @awest813

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