feat(admin-console): Stage 2 — dashboard monitoring

Turn the console landing page into an operational dashboard.

- new internal/opsstatus: read-only Postgres projection via go-jet — ping +
  per-status COUNT/GROUP BY on runtime_records, mail_deliveries,
  notification_routes, and a malformed-intent count; degrades per-probe into
  Snapshot.Errors rather than failing the page
- dashboard renders backend readiness, database health, the three status
  tables, the malformed count, and any collection errors; falls back to a
  "monitoring not wired" note when no reader is injected
- AdminConsoleHandlers now takes an AdminConsoleDeps struct (Monitor + Ready
  added) so later stages add service refs without churning the signature

Tests: opsstatus store test against a Postgres testcontainer (empty schema +
one enqueued delivery); dashboard render tests with a fake reader (with and
without monitoring).

Docs: ARCHITECTURE 14.1 + FUNCTIONAL 10.2.1 (+ru) describe the dashboard.
(Prometheus /metrics exporters were already enabled in dev-deploy in Stage 1.)

backend/internal/adminconsole/templates/pages/dashboard.gohtml

@@ -1,6 +1,43 @@
 {{define "content" -}}
 <h1>Dashboard</h1>
 <p class="lede">Signed in as <strong>{{.Username}}</strong>.</p>
+{{with .Data}}
+<section class="panel">
+  <h2>Health</h2>
+  <ul class="kv">
+    <li>Backend ready: {{if .BackendReady}}<span class="ok">yes</span>{{else}}<span class="bad">no</span>{{end}}</li>
+    <li>Postgres: {{if .PostgresHealthy}}<span class="ok">healthy</span>{{else}}<span class="bad">unreachable</span>{{end}}</li>
+  </ul>
+</section>
+{{if .MonitorAvailable}}
+<div class="grid">
+  <section class="panel">
+    <h2>Game runtimes</h2>
+    {{template "statuscounts" .Runtimes}}
+  </section>
+  <section class="panel">
+    <h2>Mail deliveries</h2>
+    {{template "statuscounts" .MailDeliveries}}
+  </section>
+  <section class="panel">
+    <h2>Notification routes</h2>
+    {{template "statuscounts" .NotificationRoutes}}
+  </section>
+  <section class="panel">
+    <h2>Malformed notifications</h2>
+    <p class="bignum {{if gt .NotificationMalformed 0}}bad{{end}}">{{.NotificationMalformed}}</p>
+  </section>
+</div>
+{{if .Errors}}
+<section class="panel errors">
+  <h2>Collection errors</h2>
+  <ul>{{range .Errors}}<li>{{.}}</li>{{end}}</ul>
+</section>
+{{end}}
+{{else}}
+<p class="note">Monitoring is not wired in this deployment.</p>
+{{end}}
+{{end}}
 <section class="cards">
   <a class="card" href="/_gm/users">
     <h2>Users</h2>
@@ -20,3 +57,13 @@
   </a>
 </section>
 {{- end}}
+
+{{define "statuscounts" -}}
+{{if .}}
+<table class="counts"><tbody>
+{{range .}}<tr><td>{{.Status}}</td><td class="num">{{.Count}}</td></tr>{{end}}
+</tbody></table>
+{{else}}
+<p class="note">none</p>
+{{end}}
+{{- end}}