feat: practice mode against mock bots

Tier-selectable practice page at /practice. Fights against classic
bots with dampened Elo. Routes to human fight page or arena based
on bot type.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/router.ts

@@ -81,6 +81,11 @@ const routes = [
     name: 'tournament',
     component: () => import('./pages/TournamentPage.vue'),
   },
+  {
+    path: '/practice',
+    name: 'practice',
+    component: () => import('./pages/PracticePage.vue'),
+  },
 ]
 
 export const router = createRouter({