feat(admin): profile freshness panel in data-quality (#81 phase B.4)

Adds a per-feature freshness summary to /admin/data-quality so the admin
can spot features that are systematically stale or never computed:

  totalEligible — distinct users with tip_views in the last 30 days
  missing       — eligible users with no row stored for the feature
  stale         — eligible users whose stored row is past its TTL

Backend exposes summarizeProfileFreshness() in profile/builder.ts; one
query per feature joins eligible users LEFT JOIN profile rows.
Coverage = (eligible − missing − stale) / eligible, colored
green/yellow/red via the new PctGood helper (high-is-good, opposite of
the existing Pct used for missing-feature/stale-token rates).

Refs #81.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

apps/admin/src/app/data-quality/page.tsx

@@ -10,6 +10,19 @@ function Pct({ value }: { value: number }) {
   return <span className={color}>{pct}%</span>;
 }
 
+function PctGood({ value }: { value: number }) {
+  const pct = (value * 100).toFixed(1);
+  const color = value > 0.95 ? 'text-green-400' : value > 0.8 ? 'text-yellow-400' : 'text-red-400';
+  return <span className={color}>{pct}%</span>;
+}
+
+function formatTtl(sec: number): string {
+  if (sec < 60) return `${sec}s`;
+  if (sec < 3600) return `${Math.round(sec / 60)}m`;
+  if (sec < 86400) return `${Math.round(sec / 3600)}h`;
+  return `${Math.round(sec / 86400)}d`;
+}
+
 export default function DataQualityPage() {
   const [data, setData] = useState<Awaited<ReturnType<typeof getDataQuality>> | null>(null);
   const [loading, setLoading] = useState(true);
@@ -50,6 +63,45 @@ export default function DataQualityPage() {
               </div>
             </div>
 
+            {/* Profile freshness — #81 phase B.4 */}
+            <div className="space-y-2">
+              <h2 className="text-sm font-medium text-gray-400">Profile feature freshness</h2>
+              <p className="text-xs text-gray-600">
+                Eligible = users with any tip activity in the last 30 days. Stale = stored row past its TTL. Missing = no row computed yet.
+              </p>
+              <table className="w-full text-xs">
+                <thead>
+                  <tr className="border-b border-gray-800 text-gray-500 text-left">
+                    <th className="py-2 pr-4">Feature</th>
+                    <th className="py-2 pr-4">TTL</th>
+                    <th className="py-2 pr-4">Eligible</th>
+                    <th className="py-2 pr-4">Missing</th>
+                    <th className="py-2 pr-4">Stale</th>
+                    <th className="py-2">Coverage</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {data.profileFreshness.map((r) => {
+                    const fresh = r.totalEligible - r.missing - r.stale;
+                    const coverage = r.totalEligible > 0 ? fresh / r.totalEligible : 0;
+                    return (
+                      <tr key={r.feature} className="border-b border-gray-800/50">
+                        <td className="py-1.5 pr-4 font-mono text-gray-400">{r.feature}</td>
+                        <td className="py-1.5 pr-4 text-gray-500 tabular-nums">{formatTtl(r.ttlSec)}</td>
+                        <td className="py-1.5 pr-4 text-gray-300 tabular-nums">{r.totalEligible}</td>
+                        <td className={`py-1.5 pr-4 tabular-nums ${r.missing > 0 ? 'text-orange-400' : 'text-gray-500'}`}>{r.missing}</td>
+                        <td className={`py-1.5 pr-4 tabular-nums ${r.stale > 0 ? 'text-yellow-400' : 'text-gray-500'}`}>{r.stale}</td>
+                        <td className="py-1.5"><PctGood value={coverage} /></td>
+                      </tr>
+                    );
+                  })}
+                  {data.profileFreshness.length === 0 && (
+                    <tr><td colSpan={6} className="py-4 text-center text-gray-600">No features registered</td></tr>
+                  )}
+                </tbody>
+              </table>
+            </div>
+
             <div className="space-y-2">
               <h2 className="text-sm font-medium text-gray-400">Daily feature completeness (14d)</h2>
               <table className="w-full text-xs">

apps/admin/src/lib/api.ts

@@ -199,6 +199,14 @@ export function getRewardAnalytics(days = 30) {
   }>(`/admin/reward-analytics?days=${days}`);
 }
 
+export interface FeatureFreshnessRow {
+  feature: string;
+  ttlSec: number;
+  totalEligible: number;
+  missing: number;
+  stale: number;
+}
+
 export function getDataQuality() {
   return apiFetch<{
     scoringCallsLast30d: number;
@@ -207,6 +215,7 @@ export function getDataQuality() {
     totalTokens: number;
     staleTokens: number;
     dailyQuality: { date: string; total: number; withFeatures: number; avgCandidates: number }[];
+    profileFreshness: FeatureFreshnessRow[];
   }>('/admin/data-quality');
 }