feat(desktop): render sent images/videos/files

desktop/src/main/index.ts

@@ -219,6 +219,15 @@ function setupIPC() {
     return result.canceled ? null : result.filePaths[0]
   })
 
+  // Open a local file with the OS default app; falls back to revealing it in
+  // the file manager when no handler exists. Returns '' on success.
+  ipcMain.handle('open-path', async (_event, targetPath: string) => {
+    if (!targetPath) return 'empty path'
+    const err = await shell.openPath(targetPath)
+    if (err) shell.showItemInFolder(targetPath)
+    return err
+  })
+
   // Custom window controls (used by Windows frameless titlebar)
   ipcMain.handle('window-minimize', () => mainWindow?.minimize())
   ipcMain.handle('window-maximize', () => {

desktop/src/main/preload.ts

@@ -6,6 +6,7 @@ contextBridge.exposeInMainWorld('electronAPI', {
   restartBackend: () => ipcRenderer.invoke('restart-backend'),
   selectDirectory: () => ipcRenderer.invoke('select-directory'),
   selectFile: (filters?: Electron.FileFilter[]) => ipcRenderer.invoke('select-file', filters),
+  openPath: (targetPath: string) => ipcRenderer.invoke('open-path', targetPath) as Promise<string>,
 
   // Each listener registrar returns an unsubscribe fn so renderers can clean
   // up on unmount / effect re-run and avoid accumulating duplicate handlers.