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/components/AdminShell.tsx

@@ -0,0 +1,58 @@
+'use client';
+
+import Link from 'next/link';
+import { usePathname } from 'next/navigation';
+
+const NAV = [
+  { href: '/', label: 'Overview' },
+  { href: '/users', label: 'Users' },
+  { href: '/events', label: 'Events' },
+  { href: '/features', label: 'Features' },
+  { href: '/tips', label: 'Rec log' },
+  { href: '/reward-analytics', label: 'Rewards' },
+  { href: '/experiments', label: 'Experiments' },
+  { href: '/models', label: 'Models' },
+  { href: '/data-quality', label: 'Data quality' },
+  { href: '/ops', label: 'Ops' },
+  { href: '/sql', label: 'SQL runner' },
+  { href: '/health', label: 'Health' },
+  { href: '/audit', label: 'Audit log' },
+  { href: '/docs', label: 'Docs' },
+];
+
+export function AdminShell({ children }: { children: React.ReactNode }) {
+  const pathname = usePathname();
+  return (
+    <div className="flex min-h-screen">
+      {/* Sidebar */}
+      <aside className="w-52 flex-shrink-0 border-r border-gray-800 bg-gray-950 flex flex-col">
+        <div className="px-5 py-4 border-b border-gray-800">
+          <span className="text-lg font-bold tracking-tight">oO</span>
+          <span className="ml-2 text-xs text-gray-500 font-medium uppercase tracking-widest">
+            Admin
+          </span>
+        </div>
+        <nav className="flex-1 px-2 py-3 space-y-0.5">
+          {NAV.map(({ href, label }) => {
+            const active = href === '/' ? pathname === '/' : pathname.startsWith(href);
+            return (
+              <Link
+                key={href}
+                href={href}
+                className={`flex items-center px-3 py-2 rounded text-sm transition-colors ${
+                  active
+                    ? 'bg-gray-800 text-white font-medium'
+                    : 'text-gray-400 hover:text-white hover:bg-gray-900'
+                }`}
+              >
+                {label}
+              </Link>
+            );
+          })}
+        </nav>
+      </aside>
+      {/* Main content */}
+      <main className="flex-1 overflow-auto p-6">{children}</main>
+    </div>
+  );
+}