v1.7.8 test (installed-only + Setup)

Test build - new since v1.7.7 pre-release:\n- Installed-only: portable .exe mode removed everywhere (Windows = Setup installer, Linux = .deb)\n- Self-update now always runs the Setup installer (silent) on Windows, .deb via password prompt on Linux\n- Compact mode fixes: copyable title/ID/version, side-by-side layout, auto-fit window\n\nWindows: run the Setup installer (per-user, no admin). Linux: sudo apt install PKGViewer-1.7.8.deb.