Fix embedded-server endpoint drift, add Recalculate All Traders button

- Shared ApiConfiguration.MapPredictalyticsEndpoints() used by both the
  standalone API and the embedded WinForms Kestrel server: the embedded
  host was missing /api/watchlist and /api/dev (empty watchlist page),
  the standalone host was missing /api/search.
- New Development menu action "Recalculate All Traders": backfills
  ResolutionOutcome from snapped outcome prices, wipes derived analytics
  (snapshots, category stats, rebuildable positions), zeroes aggregates
  and marks every trader for re-analysis. Raw trades untouched.
- Static files now served with Cache-Control: no-cache in both hosts,
  plus ?v= cache-buster on app.js/style.css (stale browser JS masked
  earlier UI fixes).
- Watchlist hardened: endpoint null-safe, real Analytics.CopytradingScore,
  Platform field; repository includes Trader.Analytics; page shows a
  visible error row instead of staying silently blank.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Predictalytics.Api/wwwroot/js/app.js

@@ -346,22 +346,26 @@ async function loadTraders() {
 }
 
 async function loadWatchlist() {
-    const data = await api(`/api/watchlist`);
-    if (!data) return;
-
     const tbody = document.getElementById('watchlistBody');
+    const data = await api(`/api/watchlist`);
+    if (!Array.isArray(data)) {
+        // api() returns null on HTTP errors — show it instead of a silently empty page.
+        tbody.innerHTML = '<tr><td colspan="8">⚠ Failed to load watchlist (see browser console / server log).</td></tr>';
+        return;
+    }
+
     tbody.innerHTML = data.map(w => `
         <tr>
             <td class="trader-name">
-                <div class="avatar">${w.displayName.substring(0, 2).toUpperCase()}</div>
+                <div class="avatar">${(w.displayName || '?').substring(0, 2).toUpperCase()}</div>
                 <div>
-                    <strong>${w.displayName}</strong><br>
-                    <span style="font-size:12px; color:var(--text-secondary)">${w.platformUserId.substring(0, 8)}...</span>
+                    <strong>${w.displayName || '?'}</strong><br>
+                    <span style="font-size:12px; color:var(--text-secondary)">${(w.platformUserId || '').substring(0, 8)}...</span>
                 </div>
             </td>
             <td>${w.platform ?? 'Unknown'}</td>
             <td>${Number(w.copytradingScore || 0).toFixed(1)}</td>
-            <td class="${w.winRate > 0.5 ? 'text-green' : 'text-red'}">${fmt.pct(w.winRate)}</td>
+            <td>${fmt.pct(w.winRate)}</td>
             <td class="${w.totalPnl >= 0 ? 'text-green' : 'text-red'}">${fmt.pnl(w.totalPnl)}</td>
             <td>${w.label || ''}</td>
             <td>${new Date(w.createdAt).toLocaleDateString()}</td>