feat: use Ubuntu native docker.io packages for Ubuntu 26.04+

Ubuntu 26.04+ ships Docker in its own repositories, so install
docker.io, docker-compose-v2, and docker-buildx directly from apt
instead of adding Docker's official repository. Falls back to the
official repo method for older Ubuntu versions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

linux-managements/install-docker.sh

@@ -555,7 +555,36 @@ do_install() {
 
 	# Run setup for each distro accordingly
 	case "$lsb_dist" in
-		ubuntu|debian|raspbian)
+		ubuntu)
+			# Check if Ubuntu version is 26.04 or higher — use native docker.io packages
+			ubuntu_major_version=""
+			if [ -r /etc/os-release ]; then
+				ubuntu_major_version="$(. /etc/os-release && echo "$VERSION_ID" | cut -d'.' -f1)"
+			fi
+			if [ -n "$ubuntu_major_version" ] && [ "$ubuntu_major_version" -ge 26 ]; then
+				echo "# Ubuntu $ubuntu_major_version detected — installing Docker from Ubuntu repositories"
+				(
+					if ! is_dry_run; then
+						set -x
+					fi
+					$sh_c 'apt-get -qq update >/dev/null'
+					# Try installing directly; if packages not found, enable Universe repo and retry
+					if ! $sh_c "DEBIAN_FRONTEND=noninteractive apt-get -y -qq install docker.io docker-compose-v2 docker-buildx >/dev/null 2>&1"; then
+						$sh_c "DEBIAN_FRONTEND=noninteractive apt-get -y -qq install software-properties-common >/dev/null"
+						$sh_c 'add-apt-repository -y universe >/dev/null'
+						$sh_c 'apt-get -qq update >/dev/null'
+						$sh_c "DEBIAN_FRONTEND=noninteractive apt-get -y -qq install docker.io docker-compose-v2 docker-buildx >/dev/null"
+					fi
+				)
+				if [ "$NO_AUTOSTART" != "1" ]; then
+					start_docker_daemon
+				fi
+				echo_docker_as_nonroot
+				exit 0
+			fi
+			# Fall through to Docker's official repository for older Ubuntu versions
+			;&
+		debian|raspbian)
 			pre_reqs="ca-certificates curl"
 			apt_repo="deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] $DOWNLOAD_URL/linux/$lsb_dist $dist_version $CHANNEL"
 			(