var. core fixes (bash to sh in fix_gpu_gids ...) (#9666)

* Switch container exec from bash to sh in fix_gpu_gids

Replaces bash with sh for container execution in fix_gpu_gids and updates device matching logic to use a POSIX-compliant case statement. This improves compatibility with containers that may not have bash installed.

* fix(apt): auto-recover from interrupted dpkg operations

When a previous installation is interrupted (e.g., by script error or
user cancellation), dpkg can be left in an inconsistent state requiring
'dpkg --configure -a' to fix.

This change:
- Adds dpkg --configure -a check to ensure_apt_working()
- Adds dpkg --configure -a to retry logic in install_packages_with_retry()
- Adds dpkg --configure -a to retry logic in upgrade_packages_with_retry()

Fixes: Omada Controller update failing after interrupted installation
Reported-in: #9663

misc/build.func

@@ -2954,15 +2954,14 @@ fix_gpu_gids() {
 
   # For privileged containers: also fix permissions inside container
   if [[ "$CT_TYPE" == "0" ]]; then
-    pct exec "$CTID" -- bash -c "
+    pct exec "$CTID" -- sh -c "
       if [ -d /dev/dri ]; then
         for dev in /dev/dri/*; do
           if [ -e \"\$dev\" ]; then
-            if [[ \"\$dev\" =~ renderD ]]; then
-              chgrp ${render_gid} \"\$dev\" 2>/dev/null || true
-            else
-              chgrp ${video_gid} \"\$dev\" 2>/dev/null || true
-            fi
+            case \"\$dev\" in
+              *renderD*) chgrp ${render_gid} \"\$dev\" 2>/dev/null || true ;;
+              *)         chgrp ${video_gid} \"\$dev\" 2>/dev/null || true ;;
+            esac
             chmod 660 \"\$dev\" 2>/dev/null || true
           fi
         done