refactor: move effects panel from global to per-track

- Added showEffects property to Track type
- Added "E" button with Sparkles icon to toggle per-track effects
- Effects panel now appears below each track when toggled
- Removed global EffectsPanel from AudioEditor
- Updated useMultiTrack to persist showEffects state
- Streamlined workflow: both automation and effects are now per-track

This aligns the UX with professional DAWs like Ableton Live, where
effects and automation are track-scoped rather than global.

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

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

components/editor/AudioEditor.tsx

@@ -14,7 +14,6 @@ import { useEffectChain } from '@/lib/hooks/useEffectChain';
 import { useToast } from '@/components/ui/Toast';
 import { TrackList } from '@/components/tracks/TrackList';
 import { ImportTrackDialog } from '@/components/tracks/ImportTrackDialog';
-import { EffectsPanel } from '@/components/effects/EffectsPanel';
 import { formatDuration } from '@/lib/audio/decoder';
 import { useHistory } from '@/lib/hooks/useHistory';
 import { useRecording } from '@/lib/hooks/useRecording';
@@ -40,8 +39,6 @@ export function AudioEditor() {
   const [punchOutTime, setPunchOutTime] = React.useState(0);
   const [overdubEnabled, setOverdubEnabled] = React.useState(false);
   const [settingsDialogOpen, setSettingsDialogOpen] = React.useState(false);
-  const [effectsPanelHeight, setEffectsPanelHeight] = React.useState(300);
-  const [effectsPanelVisible, setEffectsPanelVisible] = React.useState(false);
 
   const { addToast } = useToast();
 
@@ -816,24 +813,6 @@ export function AudioEditor() {
               trackLevels={trackLevels}
             />
           </div>
-
-          {/* Effects Panel - Global Folding State, Collapsed when no track */}
-          <EffectsPanel
-            track={selectedTrack || null}
-            visible={selectedTrack ? effectsPanelVisible : false}
-            height={effectsPanelHeight}
-            onToggleVisible={() => {
-              if (selectedTrack) {
-                setEffectsPanelVisible(!effectsPanelVisible);
-              }
-            }}
-            onResizeHeight={setEffectsPanelHeight}
-            onAddEffect={handleAddEffect}
-            onToggleEffect={handleToggleEffect}
-            onRemoveEffect={handleRemoveEffect}
-            onUpdateEffect={handleUpdateEffect}
-            onToggleEffectExpanded={handleToggleEffectExpanded}
-          />
         </main>
       </div>