Phase 3.3: Add Admin Trades page

New /admin/trades page for managing exchange trades:
- Upcoming trades tab with user contact info
- History tab with status/user search filters
- Complete/No-show/Cancel actions for admin
- Trade details: direction, amounts, rates, premium

Update navigation:
- Admin home redirects to /admin/trades
- Regular user home redirects to /exchange
- Header shows 'Trades' for admin

frontend/app/page.tsx

@@ -22,9 +22,9 @@ export default function Home() {
 
     // Redirect based on role
     if (hasRole(ADMIN)) {
-      router.replace("/admin/appointments");
+      router.replace("/admin/trades");
     } else if (hasRole(REGULAR)) {
-      router.replace("/booking");
+      router.replace("/exchange");
     } else {
       // User with no roles - redirect to login
       router.replace("/login");