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/Models/VisualizationMode.swift

@@ -0,0 +1,109 @@
+//
+//  VisualizationMode.swift
+//  PsytranceVisualizer
+//
+//  Enumeration of all available visualization modes
+//
+
+import Foundation
+
+/// Available visualization modes, accessible via keyboard shortcuts 1-8
+enum VisualizationMode: Int, CaseIterable, Codable {
+    case fftClassic = 1
+    case melSpectrogram = 2
+    case subBass = 3
+    case sidechainPump = 4
+    case hnr = 5
+    case mandelbrot = 6
+    case tunnelWarp = 7
+    case dmtGeometry = 8
+
+    /// Display name for UI
+    var displayName: String {
+        switch self {
+        case .fftClassic:
+            return "FFT Classic"
+        case .melSpectrogram:
+            return "Mel Spektrogramm"
+        case .subBass:
+            return "Sub-Bass (<100Hz)"
+        case .sidechainPump:
+            return "Sidechain Pump"
+        case .hnr:
+            return "Harmonic/Noise"
+        case .mandelbrot:
+            return "Mandelbrot"
+        case .tunnelWarp:
+            return "Tunnel Warp"
+        case .dmtGeometry:
+            return "DMT Geometry"
+        }
+    }
+
+    /// Keyboard shortcut (1-8)
+    var shortcut: String {
+        return "\(self.rawValue)"
+    }
+
+    /// Metal shader function name
+    var shaderFunctionName: String {
+        switch self {
+        case .fftClassic:
+            return "fftClassicFragment"
+        case .melSpectrogram:
+            return "melSpectrogramFragment"
+        case .subBass:
+            return "subBassFragment"
+        case .sidechainPump:
+            return "sidechainPumpFragment"
+        case .hnr:
+            return "hnrFragment"
+        case .mandelbrot:
+            return "mandelbrotFragment"
+        case .tunnelWarp:
+            return "tunnelWarpFragment"
+        case .dmtGeometry:
+            return "dmtGeometryFragment"
+        }
+    }
+
+    /// Description of the visualization
+    var description: String {
+        switch self {
+        case .fftClassic:
+            return "Classic frequency spectrum bars with glow effects"
+        case .melSpectrogram:
+            return "64-band Mel spectrogram with scrolling waterfall display"
+        case .subBass:
+            return "Pulsating rings visualizing sub-bass energy below 100Hz"
+        case .sidechainPump:
+            return "Breathing zoom effect synchronized to sidechain pumping"
+        case .hnr:
+            return "Harmonic vs noise visualization with geometric shapes"
+        case .mandelbrot:
+            return "Audio-reactive Mandelbrot fractal with zoom and color cycling"
+        case .tunnelWarp:
+            return "Infinite tunnel effect with warp distortion"
+        case .dmtGeometry:
+            return "Sacred geometry patterns: Flower of Life, Metatron's Cube, Sri Yantra"
+        }
+    }
+
+    /// Creates mode from keyboard key code
+    static func fromKeyCode(_ keyCode: UInt16) -> VisualizationMode? {
+        // Key codes for 1-8 on US keyboard
+        let keyCodes: [UInt16: Int] = [
+            18: 1,  // 1
+            19: 2,  // 2
+            20: 3,  // 3
+            21: 4,  // 4
+            23: 5,  // 5
+            22: 6,  // 6
+            26: 7,  // 7
+            28: 8   // 8
+        ]
+
+        guard let modeNumber = keyCodes[keyCode] else { return nil }
+        return VisualizationMode(rawValue: modeNumber)
+    }
+}