Show app version in sidebar, make the sidebar collapsible, and add a Light/Dark/Auto theme switch

- Expose the AeroFetch version over IPC (app:version → app.getVersion); the
  sidebar brand now shows "v<version>" beneath the name.
- Sidebar can collapse to a 60px icon-only rail via a toggle button; nav items
  and the theme control fall back to icon + tooltip when collapsed. The state is
  persisted in localStorage so it survives restarts. Hint gains left/right
  placements for the collapsed-rail tooltips.
- Replace the binary dark-mode Switch with an explicit 3-way Light / Dark / Auto
  segmented control (Auto follows the OS). Collapsed, it becomes a single button
  that cycles the three modes.
- Bump version to 0.3.2.

Verified in the browser UI preview: version label, collapse/expand, dark mode,
and the theme switch all render correctly with no console errors.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/preload/index.ts

@@ -28,6 +28,9 @@ import {
 
 // The surface exposed to the renderer. Keep this thin: it only forwards to IPC.
 const api = {
+  /** AeroFetch's own version string (e.g. '0.3.1'). */
+  getAppVersion: (): Promise<string> => ipcRenderer.invoke(IpcChannels.appVersion),
+
   getYtdlpVersion: (): Promise<YtdlpVersionResult> =>
     ipcRenderer.invoke(IpcChannels.ytdlpVersion),