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/Rendering/Shaders/SubBassShader.metal

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+//
+//  SubBassShader.metal
+//  PsytranceVisualizer
+//
+//  Pulsating rings visualizing sub-bass energy below 100Hz
+//
+
+#include <metal_stdlib>
+using namespace metal;
+
+#include "Common.metal"
+
+fragment float4 subBassFragment(
+    VertexOut in [[stage_in]],
+    constant ShaderUniforms& uniforms [[buffer(0)]],
+    constant float* fftData [[buffer(1)]],
+    constant float* melData [[buffer(2)]],
+    constant float* historyData [[buffer(3)]]
+) {
+    float2 uv = in.uv;
+    float2 resolution = uniforms.resolution;
+    float time = uniforms.time;
+    float reactivity = uniforms.reactivity;
+    float subBass = uniforms.subBassEnergy;
+
+    // Center coordinates
+    float2 center = float2(0.5, 0.5);
+    float aspectRatio = resolution.x / resolution.y;
+
+    // Correct for aspect ratio
+    float2 p = uv - center;
+    p.x *= aspectRatio;
+
+    float dist = length(p);
+    float angle = atan2(p.y, p.x);
+
+    // Main pulsating circle
+    float baseRadius = 0.15;
+    float pulseAmount = subBass * (0.5 + reactivity * 0.5);
+    float mainRadius = baseRadius + pulseAmount * 0.2;
+
+    // Add wobble based on angle
+    float wobble = sin(angle * 4.0 + time * 2.0) * 0.02 * subBass;
+    mainRadius += wobble;
+
+    // Core circle
+    float coreDist = abs(dist - mainRadius);
+    float coreGlow = exp(-coreDist * coreDist * 200.0);
+
+    // Inner fill with gradient
+    float innerFill = smoothstep(mainRadius, mainRadius * 0.3, dist);
+    innerFill *= 0.5 + 0.5 * subBass;
+
+    // Expanding rings
+    const int numRings = 6;
+    float ringIntensity = 0.0;
+
+    for (int i = 0; i < numRings; i++) {
+        // Each ring expands outward over time
+        float ringPhase = fract(time * 0.3 - float(i) * 0.15);
+        float ringRadius = mainRadius + ringPhase * 0.5;
+
+        // Get historical sub-bass value for this ring
+        int histIndex = clamp(int(ringPhase * 64.0), 0, 63);
+        float histValue = historyData[histIndex];
+
+        // Ring thickness based on historical energy
+        float thickness = 0.005 + histValue * 0.01;
+        float ringDist = abs(dist - ringRadius);
+
+        // Ring visibility
+        float ring = exp(-ringDist * ringDist / (thickness * thickness));
+        ring *= (1.0 - ringPhase); // Fade as it expands
+        ring *= histValue; // Intensity based on history
+
+        ringIntensity += ring;
+    }
+
+    // Color composition
+    float3 coreColor = mix(uvViolet, neonMagenta, subBass);
+    float3 ringColor = mix(neonMagenta, hotPink, 0.5 + 0.5 * sin(time));
+
+    float3 finalColor = float3(0.0);
+
+    // Add core
+    finalColor += coreColor * (innerFill + coreGlow * 2.0);
+
+    // Add rings
+    finalColor += ringColor * ringIntensity * 0.8;
+
+    // Add central glow
+    float centerGlow = exp(-dist * dist * 10.0) * subBass;
+    finalColor += uvViolet * centerGlow * 0.5;
+
+    // Add angular rays on peaks
+    if (uniforms.isPeak > 0.5) {
+        float rays = abs(sin(angle * 8.0 + time * 5.0));
+        rays = pow(rays, 4.0) * exp(-dist * 2.0);
+        rays *= uniforms.peakIntensity;
+        finalColor += neonCyan * rays * 0.5;
+    }
+
+    // Outer vignette
+    float vignette = 1.0 - smoothstep(0.3, 0.8, dist);
+    finalColor *= vignette;
+
+    // Background pulse
+    float bgPulse = subBass * 0.1;
+    finalColor += deepPurple * bgPulse;
+
+    // Add noise texture for organic feel
+    float noiseVal = noise(p * 20.0 + time);
+    finalColor += uvViolet * noiseVal * 0.02 * subBass;
+
+    return float4(finalColor, 1.0);
+}