feat: M1 admin console — all 10 remaining pages + signal/quality/ops infrastructure

Admin console (issues #63–72):
- Event stream viewer: live-tail ring buffer (500 events) with subject/user filters
- Feature store browser: per-user feature vector history from ml/serving
- Model registry panel: MLflow embed at /admin/models
- Experiment dashboard: LinUCB per-user stats (pulls, reward, θ) + bandit reset
- Recommendation log: per-tip explainability (policy, score, features, latency)
- Reward analytics: daily reaction breakdown + per-policy compare
- Data quality widget: missing-feature rate, stale-token rate, daily completeness
- Ops actions: replay-signal, policy enable/disable; user actions link to Users page
- SQL runner: read-only SELECT runner with saved queries
- Health rollup: fan-out to api/ml/sqlite/event-bus with auto-refresh

Backend:
- tip_scores table: logs features+policy+score+latency at every scoring call (#67)
- saved_queries table: per-admin saved SQL (#71)
- Event bus: 500-event ring buffer + tail() API (#63)
- Admin routes: /events, /tips, /reward-analytics, /data-quality, /health,
  /policies, /replay-signal, /sql, /saved-queries endpoints
- /api/ml/* admin-gated proxy to ml/serving (#64, #66)
- Shadow-policy registry in recommender (#56)

ML serving:
- /reset/{user_id}: clear bandit state + feature history (#66)
- /stats/{user_id}: pulls, cumulative reward, estimated mean, θ (#66)
- /features/{user_id}: last 100 feature vectors logged at scoring time (#64)
- Meta (pulls, rewards) persisted alongside A/b matrices

Web:
- Tip action sheet adds Helpful / Not helpful buttons (#62)
- TipFeedback type extended with helpful/not_helpful actions
- Rewards mapped: helpful=+0.5, not_helpful=−0.5

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

apps/admin/src/app/health/page.tsx

@@ -0,0 +1,71 @@
+'use client';
+
+import { useEffect, useState } from 'react';
+import { AdminShell } from '@/components/AdminShell';
+import { getHealth, HealthStatus } from '@/lib/api';
+
+const STATUS_STYLES: Record<string, string> = {
+  ok: 'bg-green-900 text-green-300 border-green-800',
+  degraded: 'bg-yellow-900 text-yellow-300 border-yellow-800',
+  down: 'bg-red-900 text-red-300 border-red-800',
+};
+
+export default function HealthPage() {
+  const [health, setHealth] = useState<HealthStatus | null>(null);
+  const [loading, setLoading] = useState(true);
+  const [error, setError] = useState('');
+
+  const refresh = () => {
+    setLoading(true);
+    getHealth()
+      .then(setHealth)
+      .catch((e) => setError(e.message))
+      .finally(() => setLoading(false));
+  };
+
+  useEffect(() => {
+    refresh();
+    const t = setInterval(refresh, 15_000);
+    return () => clearInterval(t);
+  }, []);
+
+  return (
+    <AdminShell>
+      <div className="space-y-6">
+        <div className="flex items-center justify-between">
+          <h1 className="text-xl font-semibold">Health</h1>
+          <div className="flex items-center gap-3">
+            {health && (
+              <span className={`text-xs px-2 py-1 rounded border ${health.ok ? 'bg-green-900 text-green-300 border-green-800' : 'bg-red-900 text-red-300 border-red-800'}`}>
+                {health.ok ? 'All systems operational' : 'Degraded'}
+              </span>
+            )}
+            <button onClick={refresh} className="text-xs text-gray-400 hover:text-white border border-gray-700 rounded px-2 py-1">
+              Refresh
+            </button>
+          </div>
+        </div>
+
+        {error && <p className="text-red-400 text-sm">{error}</p>}
+        {loading && !health && <p className="text-gray-500 text-sm">Checking…</p>}
+
+        {health && (
+          <>
+            <div className="grid grid-cols-2 gap-3 md:grid-cols-3 lg:grid-cols-4">
+              {health.services.map((svc) => (
+                <div key={svc.name} className={`rounded border p-4 ${STATUS_STYLES[svc.status] ?? STATUS_STYLES.down}`}>
+                  <div className="text-xs font-medium uppercase tracking-wide mb-1">{svc.name}</div>
+                  <div className="text-lg font-semibold capitalize">{svc.status}</div>
+                  {svc.latencyMs > 0 && (
+                    <div className="text-xs opacity-70 mt-1">{svc.latencyMs}ms</div>
+                  )}
+                </div>
+              ))}
+            </div>
+            <p className="text-xs text-gray-600">Last checked: {health.checkedAt} · auto-refreshes every 15s</p>
+          </>
+        )}
+      </div>
+    </AdminShell>
+  );
+}