feat(points): balance, history and shop page

Add /points page with wallet balance, shop grouped by slot and ledger
history with game names. The wallet loads once in PreferencesContext after
login, so the header shows a balance chip and the link. Premium accents
gold and teal override the free accent while equipped. German and English.

src/context/PreferencesContext.test.jsx

@@ -35,6 +35,7 @@ afterEach(() => {
 const answerMe = (settings) => fetchRoutes({
     'GET /api/users/me': json(200, {displayName: 'Lobo', settings}),
     'PUT /api/users/settings': json(204),
+    'GET /api/rewards/wallet': json(200, {balance: 0, catalog: [], owned: [], equipped: {}, history: []}),
 });
 
 describe('PreferencesProvider storage', () => {