Improve accessibility labels for screen readers

[TheZupZup]

Overview

Many controls would benefit from clearer accessibility labels / tooltips so screen readers (TalkBack) and Android accessibility tools can describe them properly. A focused, friendly first contribution.

What needs to be done

Add or improve accessibility labels for:

• Playback buttons (play/pause, next, previous, shuffle, repeat, seek)
• Cast button
• Favorite button
• Lyrics button
• Download / cache buttons
• Settings actions

Goal

Every interactive control is announced clearly by screen readers, with no "unlabeled button".

Notes

• Test with TalkBack enabled to confirm labels read sensibly.
• Keep labels concise and action-oriented (e.g. "Add to favorites", not just "Favorite").

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Suggested labels: good first issue, ui-polish, android