feat: add recalculateAllElo function for idempotent ELO recalculation

src/app/api/admin/recalculate-elo/route.ts

@@ -0,0 +1,47 @@
+import { NextResponse } from 'next/server';
+import { prisma } from '@/lib/prisma';
+import { hasRole } from '@/lib/permissions';
+import { recalculateAllElo } from '@/lib/elo-utils';
+
+/**
+ * POST /api/admin/recalculate-elo
+ * 
+ * Triggers a full recalculation of all ELO ratings and player statistics.
+ * This endpoint is idempotent - running it multiple times produces the same result.
+ * 
+ * Requires: club_admin role
+ */
+export async function POST() {
+  try {
+    // Check if user has club_admin role
+    const permission = await hasRole('club_admin');
+    if (!permission.allowed) {
+      return NextResponse.json(
+        { error: permission.reason || 'Unauthorized' },
+        { status: 403 }
+      );
+    }
+
+    // Perform the recalculation
+    const result = await recalculateAllElo(prisma);
+
+    return NextResponse.json({
+      success: true,
+      message: 'ELO recalculation completed successfully',
+      data: result,
+    });
+  } catch (error) {
+    console.error('Error during ELO recalculation:', error);
+    return NextResponse.json(
+      { error: 'Failed to recalculate ELO ratings' },
+      { status: 500 }
+    );
+  }
+}
+
+export async function GET() {
+  return NextResponse.json(
+    { error: 'Method not allowed. Use POST to trigger recalculation.' },
+    { status: 405 }
+  );
+}