Point image references at the new registry

ghcr.io went dark with the GitHub account, so every `docker pull` and
template that named it has been failing. The images are republished,
multi-arch as before, at registry.coffeylabs.org under the same names, and
pull anonymously -- nothing needs a login.

Where a link pointed at an issue list, it now goes to /-/work_items: in
GitLab 19 that is the public list, and /-/issues returns 404 to anyone not
signed in. Issues themselves did not come across from GitHub, so a link to
a specific old issue is replaced with a note saying where it was.

docker-compose.yml

@@ -8,7 +8,7 @@
 # docker-compose.host.yml (host networking) and which host sysctls matter.
 services:
   ihasvpn:
-    image: ghcr.io/coffey-labs/ihasvpn:latest
+    image: registry.coffeylabs.org/coffey-labs/ihasvpn:latest
     container_name: ihasvpn
     restart: unless-stopped
     cap_add: