feat(library): add ordered backlog page and up-next dashboard tile

src/pages/Dashboard.test.jsx

@@ -33,6 +33,7 @@ const dashboardRoutes = (settings) => ({
     'GET /api/library/activity': json(200, {totalMinutes: 90, days: [{day: '2026-09-23', minutes: 0}, {day: '2026-09-24', minutes: 90}], recentGames: [
         {appid: 1086940, name: "Baldur's Gate 3", playtimeMinutes: 900, playtime2Weeks: 90, status: 'PLAYING'}]}),
     'GET /api/library/games-count': json(200, {count: 1, hasSteamId: true}),
+    'GET /api/library/backlog': json(200, {games: [{appid: 7, name: 'Hades'}]}),
     'GET /api/library/achievements/summary': json(200, {unlocked: 24, startedGames: 4, perfectGames: 2,
         averageCompletion: 71.3, pendingGames: 0, hiddenGames: 0, closest: []}),
     'PUT /api/users/settings/dashboard-tiles': json(204, {}),
@@ -85,7 +86,7 @@ describe('Dashboard', () => {
         const container = mockDashboard();
 
         await screen.findByText('DASHBOARD.ACHIEVEMENTS.TITLE');
-        expect(order(container)).toEqual(['GAME_COUNT', 'MOST_PLAYED', 'PLAYING', 'PILE_OF_SHAME', 'ACTIVITY', 'ACHIEVEMENTS']);
+        expect(order(container)).toEqual(['GAME_COUNT', 'MOST_PLAYED', 'PLAYING', 'UP_NEXT', 'PILE_OF_SHAME', 'ACTIVITY', 'ACHIEVEMENTS']);
         expect(screen.getByText('Game 4')).toBeTruthy();
         expect(screen.queryByText('Game 5')).toBeNull();
     });
@@ -213,6 +214,7 @@ describe('Dashboard', () => {
             'GET /api/library/stats': json(200, empty),
             'GET /api/users/me': json(200, {email: 'a@b.de', displayName: 'Lobo'}),
             'GET /api/library/games-count': json(200, {count: 1, hasSteamId: true}),
+            'GET /api/library/backlog': json(200, {games: []}),
             'GET /api/library/games': (url) => (mostPlayed(url)
                 ? {ok: true, status: 200, json: async () => { throw new SyntaxError('Unexpected token <'); }}
                 : json(200, empty)),