feat: complete Phase 7.4 - real-time track effects system

Implemented comprehensive real-time effect processing for multi-track audio:

Core Features:
- Per-track effect chains with drag-and-drop reordering
- Effect bypass/enable toggle per effect
- Real-time parameter updates (filters, dynamics, time-based, distortion, bitcrusher, pitch, timestretch)
- Add/remove effects during playback without interruption
- Effect chain persistence via localStorage
- Automatic playback stop when tracks are deleted

Technical Implementation:
- Effect processor with dry/wet routing for bypass functionality
- Real-time effect parameter updates using AudioParam setValueAtTime
- Structure change detection for add/remove/reorder operations
- Stale closure fix using refs for latest track state
- ScriptProcessorNode for bitcrusher, pitch shifter, and time stretch
- Dual-tap delay line for pitch shifting
- Overlap-add synthesis for time stretching

UI Components:
- EffectBrowser dialog with categorized effects
- EffectDevice component with parameter controls
- EffectParameters for all 19 real-time effect types
- Device rack with horizontal scrolling (Ableton-style)

Removed offline-only effects (normalize, fadeIn, fadeOut, reverse) as they don't fit the real-time processing model.

Completed all items in Phase 7.4:
- [x] Per-track effect chain
- [x] Effect rack UI
- [x] Effect bypass per track
- [x] Real-time effect processing during playback
- [x] Add/remove effects during playback
- [x] Real-time parameter updates
- [x] Effect chain persistence

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/audio/effects/chain.ts

@@ -25,11 +25,6 @@ import type { FilterOptions } from './filters';
 
 // Effect type identifier
 export type EffectType =
-  // Basic
-  | 'normalize'
-  | 'fadeIn'
-  | 'fadeOut'
-  | 'reverse'
   // Filters
   | 'lowpass'
   | 'highpass'
@@ -116,7 +111,7 @@ export function createEffect(
     type,
     name,
     enabled: true,
-    parameters,
+    parameters: parameters || getDefaultParameters(type),
   };
 }
 
@@ -230,14 +225,63 @@ export function loadPreset(preset: EffectPreset): EffectChain {
   return JSON.parse(JSON.stringify(preset.chain)); // Deep clone
 }
 
+/**
+ * Get default parameters for an effect type
+ */
+export function getDefaultParameters(type: EffectType): EffectParameters {
+  switch (type) {
+    // Filters
+    case 'lowpass':
+    case 'highpass':
+      return { frequency: 1000, Q: 1 } as FilterOptions;
+    case 'bandpass':
+    case 'notch':
+      return { frequency: 1000, Q: 1 } as FilterOptions;
+    case 'lowshelf':
+    case 'highshelf':
+      return { frequency: 1000, Q: 1, gain: 0 } as FilterOptions;
+    case 'peaking':
+      return { frequency: 1000, Q: 1, gain: 0 } as FilterOptions;
+
+    // Dynamics
+    case 'compressor':
+      return { threshold: -24, ratio: 4, attack: 0.003, release: 0.25, knee: 30, makeupGain: 0 } as CompressorParameters;
+    case 'limiter':
+      return { threshold: -3, attack: 0.001, release: 0.05, makeupGain: 0 } as LimiterParameters;
+    case 'gate':
+      return { threshold: -40, ratio: 10, attack: 0.001, release: 0.1, knee: 0 } as GateParameters;
+
+    // Time-based
+    case 'delay':
+      return { time: 0.5, feedback: 0.3, mix: 0.5 } as DelayParameters;
+    case 'reverb':
+      return { roomSize: 0.5, damping: 0.5, mix: 0.3 } as ReverbParameters;
+    case 'chorus':
+      return { rate: 1.5, depth: 0.002, mix: 0.5 } as ChorusParameters;
+    case 'flanger':
+      return { rate: 0.5, depth: 0.002, feedback: 0.5, mix: 0.5 } as FlangerParameters;
+    case 'phaser':
+      return { rate: 0.5, depth: 0.5, stages: 4, mix: 0.5 } as PhaserParameters;
+
+    // Advanced
+    case 'distortion':
+      return { drive: 0.5, type: 'soft', output: 0.7, mix: 1 } as DistortionParameters;
+    case 'pitch':
+      return { semitones: 0, cents: 0, mix: 1 } as PitchShifterParameters;
+    case 'timestretch':
+      return { rate: 1.0, preservePitch: false, mix: 1 } as TimeStretchParameters;
+    case 'bitcrusher':
+      return { bitDepth: 8, sampleRate: 8000, mix: 1 } as BitcrusherParameters;
+
+    default:
+      return {};
+  }
+}
+
 /**
  * Get effect display name
  */
 export const EFFECT_NAMES: Record<EffectType, string> = {
-  normalize: 'Normalize',
-  fadeIn: 'Fade In',
-  fadeOut: 'Fade Out',
-  reverse: 'Reverse',
   lowpass: 'Low-Pass Filter',
   highpass: 'High-Pass Filter',
   bandpass: 'Band-Pass Filter',