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>

components/tracks/TrackList.tsx

@@ -124,6 +124,15 @@ export function TrackList({
               };
               onUpdateTrack(track.id, { effectChain: updatedChain });
             }}
+            onUpdateEffect={(effectId, parameters) => {
+              const updatedChain = {
+                ...track.effectChain,
+                effects: track.effectChain.effects.map((e) =>
+                  e.id === effectId ? { ...e, parameters } : e
+                ),
+              };
+              onUpdateTrack(track.id, { effectChain: updatedChain });
+            }}
             onAddEffect={(effectType) => {
               const newEffect = createEffect(
                 effectType,