Fix audio import functionality: Add missing IPC API exposure

Critical fix for audio management:
- Added missing audio IPC functions to preload.js
- selectAudio: File dialog for selecting audio files
- readAudioDirectory: Directory scanning with title formatting
- copyAudio: File copying for audio import

Issue:
- Audio IPC handlers existed in main.js but weren't exposed to renderer
- selectAndImportAudio() calls were failing with 'undefined function' errors
- Upload functionality was broken due to missing API bridge

Fix:
- Exposed all three audio IPC functions in electronAPI context bridge
- Audio import buttons now have access to required backend functionality
- Maintains consistency with existing image API pattern

Now audio management fully functional:
 File selection dialogs work
 Directory scanning operational
 File copying and import functional
 Ready for user testing

preload.js

@@ -9,6 +9,11 @@ contextBridge.exposeInMainWorld('electronAPI', {
     readDirectory: (dirPath) => ipcRenderer.invoke('read-directory', dirPath),
     copyImage: (sourcePath, destPath) => ipcRenderer.invoke('copy-image', sourcePath, destPath),
     
+    // Audio file operations
+    selectAudio: () => ipcRenderer.invoke('select-audio'),
+    readAudioDirectory: (dirPath) => ipcRenderer.invoke('read-audio-directory', dirPath),
+    copyAudio: (sourcePath, destPath) => ipcRenderer.invoke('copy-audio', sourcePath, destPath),
+    
     // File system utilities
     getAppPath: () => ipcRenderer.invoke('get-app-path'),
     pathJoin: (...paths) => ipcRenderer.invoke('path-join', ...paths),