Name the two modules after their software: nftables and distribution

A module's identity is the software it is (ADR 0040). Two were named after the
job instead, and the job already had a name.

firewall installs the nftables package and runs nftables.service. The seat it
claims is the-packet-filter, which is correctly named for the role. Calling the
module firewall named neither the software nor the provision, and promised that
any firewall could sit there — the false genericity the naming rule forbids.

registry runs Distribution, the OCI reference implementation, and provides
artifact-store. So registry was a third name for a thing that already had two,
which is how one word ended up meaning the module, the software and the concept
in the same paragraph.

The capability stays firewall, and correctly: a capability IS a functionality, so
a node having one and fail2ban requiring one are both right. Only the module
moves.

Claude-Session: https://claude.ai/code/session_01D6qtiYU3P9jk3pnAXyAFyx

modules/distribution/module.json

@@ -1,5 +1,5 @@
 {
-  "module": "registry",
+  "module": "distribution",
   "version": "1",
   "provides": [
     {

modules/nftables/module.json

@@ -1,5 +1,5 @@
 {
-  "module": "firewall",
+  "module": "nftables",
   "version": "1",
   "capabilities": [
     "firewall"

modules/showcase/module.json

@@ -43,7 +43,7 @@
     { "id": "state", "type": "directory", "path": "/var/lib/showcase", "mode": "0755" },
 
     { "id": "settings", "type": "file", "path": "/var/lib/showcase/showcase.env", "mode": "0600",
-      "content": "SHOWCASE_GREETING=hello\nSHOWCASE_EVERY_SECONDS=30\nSHOWCASE_STATE=/var/lib/showcase\nSHOWCASE_DATABASE=${bound:postgres-database:at}\n" },
+      "content": "SHOWCASE_GREETING=hello\nSHOWCASE_EVERY_SECONDS=30\nSHOWCASE_STATE=/var/lib/showcase\nSHOWCASE_DATABASE=${bound:postgres-database:at}\nSHOWCASE_LISTEN=${port:8080}\n" },
 
     { "id": "packed", "type": "archive", "path": "/opt/showcase", "artifact": "files" },