Add genlocke creation wizard with backend API and 4-step frontend

Implements the genlocke creation feature end-to-end: Genlocke and
GenlockeLeg models with migration, POST /genlockes endpoint that
creates the genlocke with all legs and auto-starts the first run,
and a 4-step wizard UI (Name, Select Games with preset templates,
Rules, Confirm) at /genlockes/new.

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

frontend/src/App.tsx

@@ -1,7 +1,7 @@
 import { Routes, Route, Navigate } from 'react-router-dom'
 import { Layout } from './components'
 import { AdminLayout } from './components/admin'
-import { Home, NewRun, RunList, RunEncounters, Stats } from './pages'
+import { Home, NewGenlocke, NewRun, RunList, RunEncounters, Stats } from './pages'
 import {
   AdminGames,
   AdminGameDetail,
@@ -19,6 +19,7 @@ function App() {
         <Route path="runs" element={<RunList />} />
         <Route path="runs/new" element={<NewRun />} />
         <Route path="runs/:runId" element={<RunEncounters />} />
+        <Route path="genlockes/new" element={<NewGenlocke />} />
         <Route path="stats" element={<Stats />} />
         <Route path="runs/:runId/encounters" element={<Navigate to=".." relative="path" replace />} />
         <Route path="admin" element={<AdminLayout />}>