Add RQuickShare Pi

## Summary Adds RQuickShare Pi as an install-based ARM64 desktop app. RQuickShare Pi is a Raspberry Pi OS ARM64-focused Quick Share desktop app for sending and receiving files with Android Quick Share devices. It uses a GUI, tray behavior, Bluetooth discovery, and mDNS networking. ## App Type Install-based app with `install-64` only. ARM64-only apps are allowed per the 2026 update in the app eligibility rubric. ## Files - `apps/RQuickShare Pi/icon-64.png` - `apps/RQuickShare Pi/icon-24.png` - `apps/RQuickShare Pi/website` - `apps/RQuickShare Pi/description` - `apps/RQuickShare Pi/credits` - `apps/RQuickShare Pi/install-64` - `apps/RQuickShare Pi/uninstall` - `etc/categories` ## Install Behavior The install script uses `install_packages` to install: - `bluez` - `avahi-daemon` - the public ARM64 `.deb` release from GitHub It then tries to enable/start Bluetooth and Avahi so discovery works after install. ## Uninstall Behavior The uninstall script stops the app if running, removes stale autostart launchers, and calls `purge_packages`. It leaves user settings and received files untouched. ## Validation - `bash -n 'apps/RQuickShare Pi/install-64' 'apps/RQuickShare Pi/uninstall'` - `shellcheck 'apps/RQuickShare Pi/install-64' 'apps/RQuickShare Pi/uninstall'` - `identify 'apps/RQuickShare Pi/icon-64.png' 'apps/RQuickShare Pi/icon-24.png'` - Pi-Apps API detected `script_name=install-64` - Release `.deb` URL responds successfully