Feat: Parametric EQ with Preset Management

[Guracc]

Summary

Adds a fully parametric equalizer mode with persistent preset management.

Features

• Parametric EQ Mode: Up to 64 bands with Peak, Low Shelf, and High Shelf filters
• Preset Management: Create, edit, and delete presets with JSON persistence
• Import Workflow: Text paste or file import via standalone window
• UI: Mode switcher, preset picker, edit (pencil) and delete (trash) buttons

Technical

• Thread-safe, lock-free audio processing
• NaN detection with automatic filter reset
  • An issue occured also in the original application
• Fixed-topology vDSP_biquad (zero allocations during updates)
• See CHANGES.md for full architecture details

Testing

• Manual testing of preset import/edit/delete workflow
• Verified audio stability under rapid parameter changes
• Verified audio stability under rapid ON/OFF switching of the EQ (I fixed some bugs that may be from the original application)

[FelikZ]

wow

[FelikZ]

@ronitsingh10 sounds like essential features here!

[FelikZ]

@Guracc build it from source, and there is no sound on 26.3.1 🤔 The visualizer moving though, when something is playing.
Audio permissions ✅