Add Map screen to App — replace placeholder with Map component

src/App.jsx

@@ -2,6 +2,7 @@ import { useState, useEffect } from 'react'
 import { generateToken, loadState, saveState } from './api.js'
 import { createState } from './gameState.js'
 import Ledger from './screens/Ledger.jsx'
+import Map from './screens/Map.jsx'
 import './App.css'
 
 const TOKEN_KEY = 'otivm_token'
@@ -71,9 +72,7 @@ export default function App() {
           <Ledger state={state} onStateChange={onStateChange} />
         </div>
         <div style={{ display: screen === 'map' ? 'block' : 'none' }}>
-          <div className="placeholder">
-            <p>Map — coming in OTIVM-II</p>
-          </div>
+          <Map state={state} />
         </div>
       </div>
     </div>