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/AudioAnalysisData.swift

@@ -0,0 +1,111 @@
+//
+//  AudioAnalysisData.swift
+//  PsytranceVisualizer
+//
+//  Audio analysis data structure containing all DSP results
+//
+
+import Foundation
+
+/// Contains all audio analysis data computed by DSPEngine
+struct AudioAnalysisData {
+    // MARK: - FFT Data
+
+    /// Raw FFT magnitude spectrum
+    var fftMagnitudes: [Float]
+
+    // MARK: - Mel Spectrogram
+
+    /// 64 Mel frequency bands
+    var melBands: [Float]
+
+    // MARK: - Sub-Bass Analysis
+
+    /// RMS energy below 100Hz (0.0 - 1.0)
+    var subBassEnergy: Float
+
+    /// History buffer for time-based visualization
+    var subBassHistory: [Float]
+
+    // MARK: - Sidechain Detection
+
+    /// Current envelope follower value (0.0 - 1.0)
+    var sidechainEnvelope: Float
+
+    /// Detected pumping amount (0.0 - 1.0)
+    var sidechainPumpAmount: Float
+
+    /// Whether pump is currently active
+    var isPumping: Bool
+
+    // MARK: - Harmonic-to-Noise Ratio
+
+    /// HNR ratio (0.0 = noise, 1.0 = pure harmonic)
+    var hnrRatio: Float
+
+    // MARK: - Transient Detection
+
+    /// Whether a transient peak was detected
+    var isPeak: Bool
+
+    /// Intensity of the detected peak (0.0 - 1.0)
+    var peakIntensity: Float
+
+    // MARK: - Stereo Channels
+
+    /// Left channel samples
+    var leftChannel: [Float]
+
+    /// Right channel samples
+    var rightChannel: [Float]
+
+    // MARK: - Additional Analysis
+
+    /// Spectral centroid (brightness) normalized 0.0 - 1.0
+    var spectralCentroid: Float
+
+    /// Overall RMS level
+    var rmsLevel: Float
+
+    // MARK: - Initialization
+
+    /// Creates an empty AudioAnalysisData with default values
+    static var empty: AudioAnalysisData {
+        AudioAnalysisData(
+            fftMagnitudes: [],
+            melBands: Array(repeating: 0, count: 64),
+            subBassEnergy: 0,
+            subBassHistory: [],
+            sidechainEnvelope: 0,
+            sidechainPumpAmount: 0,
+            isPumping: false,
+            hnrRatio: 0.5,
+            isPeak: false,
+            peakIntensity: 0,
+            leftChannel: [],
+            rightChannel: [],
+            spectralCentroid: 0.5,
+            rmsLevel: 0
+        )
+    }
+
+    /// Creates AudioAnalysisData with specified FFT size
+    static func create(fftSize: Int) -> AudioAnalysisData {
+        AudioAnalysisData(
+            fftMagnitudes: Array(repeating: 0, count: fftSize / 2),
+            melBands: Array(repeating: 0, count: 64),
+            subBassEnergy: 0,
+            subBassHistory: Array(repeating: 0, count: 128),
+            sidechainEnvelope: 0,
+            sidechainPumpAmount: 0,
+            isPumping: false,
+            hnrRatio: 0.5,
+            isPeak: false,
+            peakIntensity: 0,
+            leftChannel: [],
+            rightChannel: [],
+            spectralCentroid: 0.5,
+            rmsLevel: 0
+        )
+    }
+}