feat: disable localStorage persistence and add auto-load last project

**useMultiTrack.ts:**
- Removed localStorage persistence (tracks, effects, automation)
- Now relies entirely on IndexedDB via project management system
- Simpler state management without dual persistence

**AudioEditor.tsx:**
- Store last project ID in localStorage when saving
- Auto-load last project on page mount
- Only runs once per session with hasAutoLoaded flag
- Falls back to empty state if project can't be loaded

**Benefits:**
- No more conflicts between localStorage and IndexedDB
- Effects and automation properly persisted
- Seamless experience - reload page and your project is ready
- Single source of truth (IndexedDB)

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

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

components/editor/AudioEditor.tsx

@@ -911,6 +911,9 @@ export function AudioEditor() {
 
       setCurrentProjectId(projectId);
 
+      // Save last project ID to localStorage for auto-load on next visit
+      localStorage.setItem('audio-ui-last-project', projectId);
+
       addToast({
         title: 'Project Saved',
         description: `"${currentProjectName}" saved successfully`,
@@ -1009,6 +1012,29 @@ export function AudioEditor() {
     }
   }, [loadTracks, addToast]);
 
+  // Auto-load last project on mount
+  const [hasAutoLoaded, setHasAutoLoaded] = React.useState(false);
+  React.useEffect(() => {
+    if (hasAutoLoaded) return; // Only run once
+
+    const loadLastProject = async () => {
+      const lastProjectId = localStorage.getItem('audio-ui-last-project');
+      if (lastProjectId) {
+        try {
+          console.log('[Auto-load] Loading last project:', lastProjectId);
+          await handleLoadProject(lastProjectId);
+        } catch (error) {
+          console.error('[Auto-load] Failed to load last project:', error);
+          // Clear invalid project ID
+          localStorage.removeItem('audio-ui-last-project');
+        }
+      }
+      setHasAutoLoaded(true);
+    };
+
+    loadLastProject();
+  }, [hasAutoLoaded, handleLoadProject]);
+
   // Delete project
   const handleDeleteProject = React.useCallback(async (projectId: string) => {
     try {

lib/hooks/useMultiTrack.ts

@@ -1,79 +1,10 @@
-import { useState, useCallback, useEffect } from 'react';
+import { useState, useCallback } from 'react';
 import type { Track } from '@/types/track';
 import { createTrack, createTrackFromBuffer } from '@/lib/audio/track-utils';
-import { createEffectChain } from '@/lib/audio/effects/chain';
-import { DEFAULT_TRACK_HEIGHT } from '@/types/track';
-
-const STORAGE_KEY = 'audio-ui-multi-track';
 
 export function useMultiTrack() {
-  const [tracks, setTracks] = useState<Track[]>(() => {
-    if (typeof window === 'undefined') return [];
-
-    try {
-      const saved = localStorage.getItem(STORAGE_KEY);
-      if (saved) {
-        const parsed = JSON.parse(saved);
-
-        // Clear corrupted data immediately if we detect issues
-        const hasInvalidData = parsed.some((t: any) =>
-          typeof t.name !== 'string' || t.name === '[object Object]'
-        );
-
-        if (hasInvalidData) {
-          console.warn('Detected corrupted track data in localStorage, clearing...');
-          localStorage.removeItem(STORAGE_KEY);
-          return [];
-        }
-
-        // Note: AudioBuffers can't be serialized, but EffectChains and Automation can
-        return parsed.map((t: any) => ({
-          ...t,
-          name: String(t.name || 'Untitled Track'), // Ensure name is always a string
-          height: t.height && t.height >= DEFAULT_TRACK_HEIGHT ? t.height : DEFAULT_TRACK_HEIGHT, // Migrate old heights
-          audioBuffer: null, // Will need to be reloaded
-          effectChain: t.effectChain || createEffectChain(`${t.name} Effects`), // Restore effect chain or create new
-          automation: t.automation || { lanes: [], showAutomation: false }, // Restore automation or create new
-          selection: t.selection || null, // Initialize selection
-          showEffects: t.showEffects || false, // Restore showEffects state
-        }));
-      }
-    } catch (error) {
-      console.error('Failed to load tracks from localStorage:', error);
-      // Clear corrupted data
-      localStorage.removeItem(STORAGE_KEY);
-    }
-
-    return [];
-  });
-
-  // Save tracks to localStorage (without audio buffers)
-  useEffect(() => {
-    if (typeof window === 'undefined') return;
-
-    try {
-      // Only save serializable fields, excluding audioBuffer and any DOM references
-      const trackData = tracks.map((track) => ({
-        id: track.id,
-        name: String(track.name || 'Untitled Track'),
-        color: track.color,
-        height: track.height,
-        volume: track.volume,
-        pan: track.pan,
-        mute: track.mute,
-        solo: track.solo,
-        recordEnabled: track.recordEnabled,
-        collapsed: track.collapsed,
-        selected: track.selected,
-        showEffects: track.showEffects, // Save effects panel state
-        effectChain: track.effectChain, // Save effect chain
-        automation: track.automation, // Save automation data
-      }));
-      localStorage.setItem(STORAGE_KEY, JSON.stringify(trackData));
-    } catch (error) {
-      console.error('Failed to save tracks to localStorage:', error);
-    }
-  }, [tracks]);
+  // Note: localStorage persistence disabled in favor of IndexedDB project management
+  const [tracks, setTracks] = useState<Track[]>([]);
 
   const addTrack = useCallback((name?: string) => {
     const track = createTrack(name);