fix(docker): use fully-qualified docker.io image refs; mark T07 done

Prefix all image names with docker.io/ to avoid registry ambiguity
on hosts where containerd/Podman default to docker.io but the pull
fails without an explicit registry prefix.

Also marks T07 (smoke-test Temporal cluster and UI) as done in the
workplan now that the stack boots cleanly.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.dev.yml

@@ -19,7 +19,7 @@ services:
   # ── Temporal persistence store ────────────────────────────────────────────────
   temporal-db:
     container_name: temporal-db
-    image: postgres:16.6
+    image: docker.io/postgres:16.6
     environment:
       POSTGRES_USER: temporal
       POSTGRES_PASSWORD: temporal
@@ -39,7 +39,7 @@ services:
   # ── Elasticsearch (Temporal visibility store) ─────────────────────────────────
   elasticsearch:
     container_name: temporal-elasticsearch
-    image: elasticsearch:7.17.27
+    image: docker.io/elasticsearch:7.17.27
     environment:
       - cluster.routing.allocation.disk.threshold_enabled=true
       - cluster.routing.allocation.disk.watermark.low=512mb
@@ -63,7 +63,7 @@ services:
   # ── Temporal server ───────────────────────────────────────────────────────────
   temporal:
     container_name: temporal
-    image: temporalio/auto-setup:1.29.1
+    image: docker.io/temporalio/auto-setup:1.29.1
     depends_on:
       temporal-db:
         condition: service_healthy
@@ -97,7 +97,7 @@ services:
   # ── Temporal Web UI ───────────────────────────────────────────────────────────
   temporal-ui:
     container_name: temporal-ui
-    image: temporalio/ui:2.34.0
+    image: docker.io/temporalio/ui:2.34.0
     depends_on:
       temporal:
         condition: service_healthy
@@ -112,7 +112,7 @@ services:
   # ── Temporal admin tools (shell access for debugging) ─────────────────────────
   temporal-admin-tools:
     container_name: temporal-admin-tools
-    image: temporalio/admin-tools:1.29.1-tctl-1.18.4-cli-1.5.0
+    image: docker.io/temporalio/admin-tools:1.29.1-tctl-1.18.4-cli-1.5.0
     depends_on:
       temporal:
         condition: service_healthy
@@ -127,7 +127,7 @@ services:
   # ── App database (activity-core application data) ─────────────────────────────
   app-db:
     container_name: actcore-app-db
-    image: postgres:16.6
+    image: docker.io/postgres:16.6
     environment:
       POSTGRES_USER: actcore
       POSTGRES_PASSWORD: actcore