Add Theme Builder panel with live color presets

[Copilot]

Description

Adds an in-editor theme builder so users can switch UI themes from presets and fine-tune colors in real time.
This addresses the request for a theme builder with presets by making theme state runtime-configurable and immediately reflected across custom painting and JUCE component styling.

• Theme system refactor

  • Introduced CyberpunkLookAndFeel::ThemePalette and runtime applyTheme()/getTheme().
  • Replaced hardcoded color usage in custom draw paths with active theme values.

• Theme Builder UI

  • Added a dedicated THEME BUILDER panel in PluginEditor.
  • Added preset selector: Matrix Green, Cyan Pulse, Magenta Glow, Amber Terminal, Custom.
  • Added Hue/Saturation/Brightness controls for custom palette tuning.

• Live update wiring

  • Preset selection applies full palette immediately.
  • H/S/B edits auto-switch to Custom and repaint instantly.
  • Control-to-theme synchronization keeps sliders aligned with active palette.

themePresetCombo.addItem("Matrix Green", themePresetMatrix);
themePresetCombo.addItem("Cyan Pulse", themePresetCyan);
themePresetCombo.addItem("Magenta Glow", themePresetMagenta);
themePresetCombo.addItem("Amber Terminal", themePresetAmber);
themePresetCombo.addItem("Custom", themePresetCustom);

cyberpunkLF.applyTheme(makeThemeFromHSB(h, s, b));
repaint();

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Performance improvement
• Code refactoring

Testing

• Tested in DAW (specify which one):
• Verified VST3 functionality
• Verified AU functionality (macOS only)
• Tested on platform(s):

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• Any dependent changes have been merged and published

Screenshots (if applicable)