Phase 3: Audio equalizer UI improvements

[KevinTCoughlin]

Enhance equalizer with visual feedback and preset management.

What:

• Visual band display (sliders or frequency spectrum)
• Pre-built presets: Normal, Bass Boost, Vocal, Treble
• Save custom presets
• Real-time audio feedback

Why: Current presets are basic. Users want to tune audio for different content.

Implementation:

• Multi-band EQ display with sliders
• Real-time Android Equalizer updates
• Preset save/load UI
• Persist to DataStore

Reference: Transistor tone adjustment (basic EQ)

Phase: 3 (Advanced) | Effort: 12-15h | Target: feature branch