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/App.tsx

@@ -1,14 +1,13 @@
 import { Routes, Route } from 'react-router-dom'
 import { Layout } from './components'
-import { Home, GameSelect, Dashboard, Encounters, Rules } from './pages'
+import { Home, NewRun, Dashboard, Encounters } from './pages'
 
 function App() {
   return (
     <Routes>
       <Route path="/" element={<Layout />}>
         <Route index element={<Home />} />
-        <Route path="games" element={<GameSelect />} />
-        <Route path="rules" element={<Rules />} />
+        <Route path="runs/new" element={<NewRun />} />
         <Route path="dashboard" element={<Dashboard />} />
         <Route path="encounters" element={<Encounters />} />
       </Route>