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/network-config.j2

@@ -0,0 +1,18 @@
+# {{ ansible_managed }} -- rendered by `make bootfs`
+#
+# Ethernet only, on purpose. Wi-Fi is NOT configured here: cloud-init renders
+# this through netplan into a persistent profile of netplan's own, which is not
+# a file this repo manages or can readily update. The Wi-Fi profiles are written
+# straight into /etc/NetworkManager/system-connections by user-data instead, so
+# the image and Ansible manage the same files.
+#
+# A card that has already booted with Wi-Fi in network-config keeps netplan's
+# profile. That is fine, and useful -- see the "Coexisting with netplan" note in
+# roles/labelprint/tasks/wifi.yml.
+network:
+  version: 2
+  ethernets:
+    eth0:
+      dhcp4: true
+      dhcp6: true
+      optional: true