Add game selection screen and new run wizard

Build a 3-step wizard at /runs/new: select game (themed gradient cards
grouped by generation with filter tabs), configure rules (reuses existing
RulesConfiguration), and name/create run. Remove standalone Games and Rules
pages since they're now integrated into the wizard flow.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/Layout.tsx

@@ -13,16 +13,10 @@ export function Layout() {
             </div>
             <div className="flex items-center space-x-4">
               <Link
-                to="/games"
+                to="/runs/new"
                 className="px-3 py-2 rounded-md text-sm font-medium hover:bg-gray-100 dark:hover:bg-gray-700"
               >
-                Games
-              </Link>
-              <Link
-                to="/rules"
-                className="px-3 py-2 rounded-md text-sm font-medium hover:bg-gray-100 dark:hover:bg-gray-700"
-              >
-                Rules
+                New Run
               </Link>
               <Link
                 to="/dashboard"