feat(security): digest-pin every registry image on all three hosts (fleet law)

Closing the command-center security queue #70/#71/#72/#73/#74: rolling tags
let a rebuild move under a running service with nobody approving it, and
make a CVE audit ungradeable. 36 quadlet units across dankclaw, dankserver
and frankbook-pro now carry tag@sha256; localhost/* builds stay exempt
(their build is the pin). The pihole and copyparty pins pull the fixed
builds; valkey 9.1.2 (already running) and redis 7.4.11 are pinned in
place, vendor fixes TBD.

New gate tests/quadlet_image_pins.bats: no unpinned registry image, no
generator-rejected key anywhere. Three seams that pinned the old exact-tag
law (frankbook readarr, open_webui, seerr) now require tag AND digest -
strictly stronger. Quadlet Lifecycle docs: batch-abort law, entrypoint
flags-only law, pin law.

tests/quadlet_image_pins.bats

@@ -0,0 +1,47 @@
+#!/usr/bin/env bats
+# Seam: fleet-wide quadlet laws learned the hard way.
+#   1. Every registry image is digest-pinned. A rolling tag (":latest",
+#      ":9-alpine", ":nightly") lets a rebuild move under a running
+#      service at the next restart/reboot with nobody approving it, and it
+#      makes a CVE audit ungradeable (you cannot score a tag). Locally
+#      built images (localhost/*, franksdank/*) are exempt: their build
+#      IS the pin, and they never pull.
+#   2. No unit carries a key the podman 5.7.0 quadlet generator rejects.
+#      The generator aborts the WHOLE batch on an unsupported key, so one
+#      bad file silently un-generates every other unit in that manager -
+#      live 2026-10-21: HostAddr= in prometheus.container orphaned
+#      prometheus.service while its container kept running, and the next
+#      deploy died on "Unit prometheus.service not found".
+
+load helpers
+
+@test "every registry Image= is digest-pinned across all three hosts" {
+    bad=""
+    while IFS= read -r unit; do
+        while IFS= read -r img; do
+            case "$img" in
+                localhost/*|franksdank/*) continue ;;
+            esac
+            case "$img" in
+                *@sha256:*) ;;
+                *) bad="$bad$unit: $img"$'\n' ;;
+            esac
+        done < <(sed -n 's/^Image=//p' "$unit")
+    done < <(find "$REPO_ROOT"/dankserver "$REPO_ROOT"/dankclaw "$REPO_ROOT"/frankbook-pro \
+                 -path '*/quadlet/*.container' -not -path '*.AGENTTRASH*')
+    [ -z "$bad" ] || { printf 'unpinned images:\n%s' "$bad" >&2; return 1; }
+}
+
+@test "no unit uses a key the 5.7.0 quadlet generator rejects (batch killer)" {
+    # HostAddr rejected by podman 5.7.0 (live 2026-10-21); Device= and
+    # Command= are the older v1 findings, guarded host-locally too.
+    # Keep this list current with every generator finding.
+    bad=""
+    while IFS= read -r unit; do
+        for key in HostAddr Device Command; do
+            grep -q "^${key}=" "$unit" && bad="$bad$unit: ${key}="$'\n'
+        done
+    done < <(find "$REPO_ROOT"/dankserver "$REPO_ROOT"/dankclaw "$REPO_ROOT"/frankbook-pro \
+                 -path '*/quadlet/*.container' -not -path '*.AGENTTRASH*')
+    [ -z "$bad" ] || { printf 'generator-rejected keys:\n%s' "$bad" >&2; return 1; }
+}