fix(updater): package installs (AUR, deb, rpm) are updated outside the app

[ZhuchkaTriplesix]

Problem

With the AUR package, Update from 0.4.18 to 0.4.19 downloaded the update, closed the app and nothing started again; a reinstall was needed.

Cause (confirmed on the affected machine)

• The AUR package (and the .deb / .rpm, scripts/linux/build_deb.sh) installs the bundle into /opt/querya-desktop, owned by root, with /usr/bin/querya_desktop as a symlink. Platform.resolvedExecutable resolves to /opt/querya-desktop/querya_desktop.
• UpdateInstallContext.isManagedPackage only knew Snap and Flatpak, so the updater treated this as a portable bundle: it downloaded Querya-Desktop-0.4.19-linux.zip, extracted it, wrote a replace script and quit the app.
• The script (set -e) could not delete or copy in /opt/querya-desktop and exited before its final exec, so the app was not restarted. The leftovers were still in /tmp: /tmp/querya-linux-update-3799797.sh (target DST='/opt/querya-desktop', it removes itself only on success) and the extracted /tmp/querya-update-1791735255359/.
• The earlier fix (bug(updater): Linux portable update wipes QueryaData folder via rm -rf / rsync --delete #1055) protected the data of portable bundles during a replace; it did not cover installs the user cannot write.

Fix

• UpdateInstallContext.linuxSystemPackageManager: pacman (an entry querya-desktop-* in /var/lib/pacman/local), dpkg (/var/lib/dpkg/info/querya-desktop.list) or rpm, only when the running bundle is /opt/querya-desktop, so a portable copy elsewhere is not affected.
• isLinuxBundleReadOnly: the bundle folder exists and the user cannot write it (a probe file), whoever installed it.
• Both make isManagedPackage true. The update dialog already handles that: no Download, a Copy update command button with yay -Syu querya-desktop, sudo apt update && sudo apt install --only-upgrade querya-desktop or sudo dnf upgrade querya-desktop; for a read-only folder of unknown origin it shows a hint and an Open release page button.
• The zip installer refuses a managed target before the app quits.
• The replace script checks [ -w "$DST" ] and, on any failure (not writable, rsync / rm / cp failing), writes the reason to ~/.local/state/querya-update.log and starts the app again instead of exiting.
• CHANGELOG [Unreleased] entry.

Checked

• The generated script passes sh -n, and I ran it against a fake bundle: with a read-only target it logs the reason and relaunches the old executable; with a writable one it installs and runs the new one and removes itself.
• Unit tests: pacman, dpkg, a portable bundle next to an installed package (not blocked), a read-only folder (blocked, hint, no command), the installer refusing a pacman install, and the script's new guard.

Note for 0.4.19 users

The updater that runs is the installed one, so this helps from the release after it: users of the AUR / .deb / .rpm 0.4.19 should still update through their package manager. Worth a line in the next release notes.