feat: add system tray with quick actions and minimize-to-tray

System tray:
- Always-visible tray icon with context menu
- Quick Scratchpad action from tray (triggers session creation
  via IPC bridge to renderer)
- Running session count in tray tooltip and menu
- Click tray icon to show/focus window
- Quit option in tray menu

Minimize to tray:
- New 'Minimize to tray on close' toggle in Settings > Appearance
- When enabled, closing the window hides to tray instead of
  quitting (configurable per-user, default off)
- macOS: hides dock icon when minimized to tray
- Proper force-quit handling (Cmd+Q on macOS, tray Quit)

Full IPC contract chain:
- minimizeToTray setting in WorkspaceSettings
- setMinimizeToTray channel + ElectronApi method
- Preload bridge, service handler, IPC registration
- Preserved through workspace normalization

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/AryxAppService.ts

@@ -514,6 +514,12 @@ export class AryxAppService extends EventEmitter<AppServiceEvents> {
     return this.persistAndBroadcast(workspace);
   }
 
+  async setMinimizeToTray(enabled: boolean): Promise<WorkspaceState> {
+    const workspace = await this.loadWorkspace();
+    workspace.settings.minimizeToTray = enabled;
+    return this.persistAndBroadcast(workspace);
+  }
+
   async describeTerminal(): Promise<TerminalSnapshot | undefined> {
     return this.ptyManager.getSnapshot();
   }