feat: add MP3 and FLAC export formats

Implemented Phase 11.1 export format support:
- Added MP3 export using lamejs library
- Added FLAC export using fflate DEFLATE compression
- Updated ExportDialog with format selector and format-specific options
  - MP3: bitrate selector (128/192/256/320 kbps)
  - FLAC: compression quality slider (0-9)
  - WAV: bit depth selector (16/24/32-bit)
- Updated AudioEditor to route export based on selected format
- Created TypeScript declarations for lamejs
- Fixed AudioStatistics to use audioBuffer instead of buffer property

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

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

pnpm-lock.yaml

@@ -11,6 +11,9 @@ importers:
       clsx:
         specifier: ^2.1.1
         version: 2.1.1
+      fflate:
+        specifier: ^0.8.2
+        version: 0.8.2
       lamejs:
         specifier: ^1.2.1
         version: 1.2.1
@@ -1085,6 +1088,9 @@ packages:
       picomatch:
         optional: true
 
+  fflate@0.8.2:
+    resolution: {integrity: sha512-cPJU47OaAoCbg0pBvzsgpTPhmhqI5eJjh/JIu8tPj5q+T7iLvW/JAYUqmE7KOB4R1ZyEhzBaIQpQpardBF5z8A==}
+
   file-entry-cache@8.0.0:
     resolution: {integrity: sha512-XXTUwCvisa5oacNGRP9SfNtYBNAMi+RPwBFmblZEF7N7swHYQS6/Zfk7SRwx4D5j3CH211YNRco1DEMNVfZCnQ==}
     engines: {node: '>=16.0.0'}
@@ -3109,6 +3115,8 @@ snapshots:
     optionalDependencies:
       picomatch: 4.0.3
 
+  fflate@0.8.2: {}
+
   file-entry-cache@8.0.0:
     dependencies:
       flat-cache: 4.0.1