feat(labelprint): 4x6 label print proxy on a Raspberry Pi

A Pi 3B+ (stickah.local) shares a Phomemo PM246 to the LAN as a plain CUPS
queue, so any machine can print 4x6 labels -- fulfillr-site's shipping labels
in particular -- without installing the vendor driver, which is x86-64 only.
The role builds the TSPL CUPS driver from source instead.

It is Debian, not Fedora, so it lives in its own inventory and playbook
(make deploy-labelprint / check-labelprint) and the home.debyl.io roles can
never run against it. make bootfs renders its cloud-init first-boot files onto
a freshly imaged SD card from the same templates the role uses. The Wi-Fi
credentials for the home and rescue networks are in the vault.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ansible/roles/labelprint/templates/bootfs/meta-data.j2

@@ -0,0 +1,11 @@
+# {{ ansible_managed }} -- rendered by `make bootfs`
+#
+# cloud-init applies user-data once per INSTANCE, not once per boot: rewrite
+# user-data on a card that has already booted and nothing happens, because
+# cloud-init recognises the instance id and skips straight to per-boot modules.
+#
+# Deriving the id from a hash of user-data itself fixes that. Re-running
+# `make bootfs` with no changes leaves the id alone, so a card keeps its
+# identity; change anything in user-data and the id changes with it, and the
+# Pi re-applies the new config on its next boot without a reflash.
+instance-id: {{ labelprint_hostname }}-{{ labelprint_user_data_id }}