Fix USB install reliability: bash, LV resize, deps, idempotency

- autoinstall/user-data: move lvextend/growpart/pvresize BEFORE playbook
  so 130GB of drivers+PPKGs fits during first-boot copy. Use
  tr -d "[:space:]" to avoid breaking outer bash -c single-quote wrap.
- playbook: add executable: /bin/bash to Dell driver deploy (process
  substitution) and Blancco initramfs builder (brace expansion).
- playbook: make "Ensure Samba user for Blancco reports" idempotent via
  pdbedit check so re-runs don't abort the play.
- download-packages.sh: also download dist-upgrade package set. Explicit
  --simulate misses transitive version bumps (e.g. gnupg 17.4 needs
  matching gpgv 17.4) causing offline dpkg "dependency problems" when
  ISO baseline is older than noble-updates.

autoinstall/user-data

@@ -72,6 +72,16 @@ autoinstall:
       curtin in-target --target=/target -- bash -c '
       cat <<"EOF" > /opt/first-boot.sh
       #!/bin/bash
+      # Expand root LV to full disk BEFORE playbook (playbook copies ~130GB of drivers+PPKGs)
+      ROOT_DEV=$(findmnt -n -o SOURCE /)
+      ROOT_DISK=$(lsblk -n -o PKNAME "$(readlink -f "$ROOT_DEV")" | tail -1)
+      PV_PART=$(pvs --noheadings -o pv_name 2>/dev/null | tr -d "[:space:]" | head -1)
+      if [ -n "$ROOT_DISK" ] && [ -n "$PV_PART" ]; then
+        PART_NUM=$(echo "$PV_PART" | grep -o "[0-9]*$")
+        growpart "/dev/${ROOT_DISK}" "${PART_NUM}" 2>&1 || true
+        pvresize "$PV_PART" 2>&1 || true
+      fi
+      lvextend -r -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv 2>&1 || true
       CIDATA_DEV=$(blkid -L CIDATA)
       if [ -n "$CIDATA_DEV" ]; then
         mkdir -p /mnt/usb
@@ -88,7 +98,6 @@ autoinstall:
         umount /mnt/usb
       fi
       sed -i "s|^/opt/first-boot.sh.*|# &|" /etc/rc.local
-      lvextend -r -l +100%FREE /dev/mapper/ubuntu--vg-ubuntu--lv || true
       EOF
       chmod +x /opt/first-boot.sh
       '