Add Settings -> Database viewer (Adminer) for local devs and any admin

Local dev gets an unauthenticated Adminer instance bound to loopback
only. In production, any account with is_admin=true can open it -
the app mints a short-lived token from a live admin session, which
Nginx's new db.ciagent.org block exchanges for a session cookie that
re-checks admin status on every request, instead of a shared static
password that wouldn't scale to multiple admins or revoke live.

Co-Authored-By: Claude Sonnet 5 <[email protected]>

docker-compose.yml

@@ -110,5 +110,18 @@ services:
     depends_on:
       - api
 
+  adminer:
+    image: adminer:4.8.1-standalone
+    restart: unless-stopped
+    environment:
+      ADMINER_DEFAULT_SERVER: postgres
+    ports:
+      # Loopback-only, matching this app's loopback-trust philosophy - not
+      # meant to be reachable from the LAN. See Settings -> Database.
+      - "127.0.0.1:8081:8080"
+    depends_on:
+      postgres:
+        condition: service_healthy
+
 volumes:
   postgres-data: