Add Psytrance Visualizer macOS app with Metal rendering

A complete audio-reactive visualizer for psytrance music featuring:

Audio Analysis (DSPEngine):
- FFT spectrum analysis via Accelerate/vDSP
- 64-band Mel spectrogram
- Sub-bass energy extraction (<100Hz)
- Automatic sidechain pump detection
- Harmonic-to-Noise ratio (HNR) calculation
- Peak/transient detection

8 Visualization Modes (Metal Shaders):
1. FFT Classic - Frequency spectrum bars with glow
2. Mel Spectrogram - Waterfall display
3. Sub-Bass - Pulsating rings
4. Sidechain Pump - Breathing zoom effect
5. Harmonic/Noise - Geometric vs chaotic particles
6. Mandelbrot - Audio-reactive fractal zoom
7. Tunnel Warp - Infinite tunnel with distortion
8. DMT Geometry - Sacred geometry patterns

Features:
- Selectable audio input device (BlackHole support)
- Configurable buffer size (512/1024)
- Reactivity slider for visual intensity
- Auto-hiding control panel
- Fullscreen support with keyboard shortcuts (1-8, F, ESC)
- Persistent settings via UserDefaults
- Psytrance-inspired neon/UV color palette

PsytranceVisualizer/Utilities/ColorPalette.swift

@@ -0,0 +1,140 @@
+//
+//  ColorPalette.swift
+//  PsytranceVisualizer
+//
+//  Psytrance color palette for UI and shaders
+//
+
+import AppKit
+import simd
+
+/// Psytrance-inspired neon/UV color palette
+struct PsytranceColors {
+    // MARK: - Primary Colors (NSColor for UI)
+
+    /// Neon Magenta - Primary accent color
+    static let neonMagenta = NSColor(red: 1.0, green: 0.0, blue: 1.0, alpha: 1.0)
+
+    /// Neon Cyan - Secondary accent color
+    static let neonCyan = NSColor(red: 0.0, green: 1.0, blue: 1.0, alpha: 1.0)
+
+    /// Neon Green - High energy accents
+    static let neonGreen = NSColor(red: 0.224, green: 1.0, blue: 0.078, alpha: 1.0)
+
+    /// UV Violet - Deep purple for backgrounds
+    static let uvViolet = NSColor(red: 0.482, green: 0.0, blue: 1.0, alpha: 1.0)
+
+    /// Deep Black - Background color
+    static let background = NSColor(red: 0.0, green: 0.0, blue: 0.0, alpha: 1.0)
+
+    /// Dark Purple - Alternative background
+    static let darkPurple = NSColor(red: 0.1, green: 0.0, blue: 0.15, alpha: 1.0)
+
+    /// Hot Pink - Peak indicators
+    static let hotPink = NSColor(red: 1.0, green: 0.2, blue: 0.6, alpha: 1.0)
+
+    /// Electric Blue - UI elements
+    static let electricBlue = NSColor(red: 0.0, green: 0.5, blue: 1.0, alpha: 1.0)
+
+    // MARK: - SIMD3<Float> Colors (for Metal shaders)
+
+    struct Metal {
+        static let neonMagenta = SIMD3<Float>(1.0, 0.0, 1.0)
+        static let neonCyan = SIMD3<Float>(0.0, 1.0, 1.0)
+        static let neonGreen = SIMD3<Float>(0.224, 1.0, 0.078)
+        static let uvViolet = SIMD3<Float>(0.482, 0.0, 1.0)
+        static let background = SIMD3<Float>(0.0, 0.0, 0.0)
+        static let darkPurple = SIMD3<Float>(0.1, 0.0, 0.15)
+        static let hotPink = SIMD3<Float>(1.0, 0.2, 0.6)
+        static let electricBlue = SIMD3<Float>(0.0, 0.5, 1.0)
+
+        /// Array of all palette colors for cycling
+        static let palette: [SIMD3<Float>] = [
+            neonMagenta,
+            neonCyan,
+            neonGreen,
+            uvViolet,
+            hotPink,
+            electricBlue
+        ]
+
+        /// Get color from palette by index (wraps around)
+        static func color(at index: Int) -> SIMD3<Float> {
+            palette[index % palette.count]
+        }
+
+        /// Interpolate between two colors
+        static func lerp(_ a: SIMD3<Float>, _ b: SIMD3<Float>, t: Float) -> SIMD3<Float> {
+            a + (b - a) * t
+        }
+
+        /// Get rainbow color from normalized value (0-1)
+        static func rainbow(_ t: Float) -> SIMD3<Float> {
+            let index = Int(t * Float(palette.count))
+            let nextIndex = (index + 1) % palette.count
+            let localT = (t * Float(palette.count)) - Float(index)
+            return lerp(palette[index % palette.count], palette[nextIndex], t: localT)
+        }
+    }
+
+    // MARK: - Gradient Helpers
+
+    /// Creates a gradient from UV Violet through Magenta to Cyan
+    static var spectrumGradient: NSGradient? {
+        NSGradient(colors: [uvViolet, neonMagenta, hotPink, neonCyan, neonGreen])
+    }
+
+    /// Creates a gradient for heat maps (low to high energy)
+    static var heatmapGradient: NSGradient? {
+        NSGradient(colors: [
+            NSColor(red: 0.1, green: 0.0, blue: 0.2, alpha: 1.0),  // Dark purple (low)
+            uvViolet,
+            neonMagenta,
+            hotPink,
+            neonCyan,
+            neonGreen,
+            NSColor.white  // White (peak)
+        ])
+    }
+
+    // MARK: - UI Theme Colors
+
+    struct UI {
+        static let panelBackground = NSColor(red: 0.05, green: 0.02, blue: 0.08, alpha: 0.9)
+        static let buttonBackground = NSColor(red: 0.15, green: 0.05, blue: 0.2, alpha: 1.0)
+        static let buttonHighlight = neonMagenta.withAlphaComponent(0.8)
+        static let sliderTint = neonCyan
+        static let labelText = NSColor.white
+        static let secondaryText = NSColor(white: 0.7, alpha: 1.0)
+        static let border = uvViolet.withAlphaComponent(0.5)
+    }
+}
+
+// MARK: - NSColor Extension
+
+extension NSColor {
+    /// Converts NSColor to SIMD3<Float> for Metal
+    var simd3: SIMD3<Float> {
+        guard let rgb = usingColorSpace(.deviceRGB) else {
+            return SIMD3<Float>(0, 0, 0)
+        }
+        return SIMD3<Float>(
+            Float(rgb.redComponent),
+            Float(rgb.greenComponent),
+            Float(rgb.blueComponent)
+        )
+    }
+
+    /// Converts NSColor to SIMD4<Float> for Metal (with alpha)
+    var simd4: SIMD4<Float> {
+        guard let rgb = usingColorSpace(.deviceRGB) else {
+            return SIMD4<Float>(0, 0, 0, 1)
+        }
+        return SIMD4<Float>(
+            Float(rgb.redComponent),
+            Float(rgb.greenComponent),
+            Float(rgb.blueComponent),
+            Float(rgb.alphaComponent)
+        )
+    }
+}