fix: remove fake FLAC export format

Removed the non-standard FLAC export option which was causing import issues:

**Problem:**
- "FLAC" export was actually a custom compressed WAV format
- Used fflate (DEFLATE compression) instead of real FLAC encoding
- Files couldn't be imported back or opened in other software
- No browser-compatible FLAC encoder library exists

**Changes:**
- Removed FLAC from export format options (WAV and MP3 only)
- Removed FLAC quality slider from ExportDialog
- Removed audioBufferToFlac function reference
- Updated ExportSettings interface to only include 'wav' | 'mp3'
- Simplified bit depth selector (WAV only instead of WAV/FLAC)
- Updated format descriptions to clarify lossy vs lossless

**Export formats now:**
- ✅ WAV - Lossless, Uncompressed (16/24/32-bit)
- ✅ MP3 - Lossy, Compressed (128/192/256/320 kbps)

Users can now successfully export and re-import their audio!

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

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

components/editor/AudioEditor.tsx

@@ -34,7 +34,7 @@ import {
 } from '@/lib/history/commands/multi-track-edit-command';
 import { extractBufferSegment } from '@/lib/audio/buffer-utils';
 import { mixTracks, getMaxTrackDuration } from '@/lib/audio/track-utils';
-import { audioBufferToWav, audioBufferToMp3, audioBufferToFlac, downloadArrayBuffer } from '@/lib/audio/export';
+import { audioBufferToWav, audioBufferToMp3, downloadArrayBuffer } from '@/lib/audio/export';
 
 export function AudioEditor() {
   const [importDialogOpen, setImportDialogOpen] = React.useState(false);
@@ -746,16 +746,8 @@ export function AudioEditor() {
           });
           mimeType = 'audio/mpeg';
           fileExtension = 'mp3';
-        } else if (settings.format === 'flac') {
-          exportedBuffer = await audioBufferToFlac(buffer, {
-            format: 'flac',
-            bitDepth: settings.bitDepth,
-            quality: settings.quality,
-            normalize: settings.normalize,
-          });
-          mimeType = 'application/octet-stream';
-          fileExtension = 'flac';
         } else {
+          // WAV export
           exportedBuffer = audioBufferToWav(buffer, {
             format: 'wav',
             bitDepth: settings.bitDepth,