v0.11.6 — tray icon moves into the daemon (persistent, Vortex-style)

The system-tray / menu-bar icon now lives in the daemon (the always-on process), not the GUI — so it's a persistent presence whenever Concierge is running, even with the window closed.

• The daemon hosts a system-tray icon (macOS menu-bar status item / Windows notification-area icon) via a small event loop on its main thread; the download server runs behind it. On macOS it's a menu-bar agent (no Dock icon).
• Menu: Open Concierge (launches a window if none is open) / Downloads: N / Quit (closes any window, then stops the daemon — the whole app stops).
• The GUI is now ephemeral: closing the window fully quits it; the daemon + tray + downloads keep running. Reopen from the tray.

Fixes the Windows report where running the daemon showed no toolbar icon — the tray was in the GUI before. Note: Windows may tuck a new tray icon into the hidden "^" overflow; drag it onto the taskbar to keep it visible.