feat(dashboard): playtime chart, recently played and a playing hint

The dashboard shows the playtime of the last 30 days and Steam's recently
played games. The detail page offers to set a backlog game to Playing when
Steam reports recent playtime; unsaved edits in the backlog card stay.

src/pages/GameDetail.test.jsx

@@ -0,0 +1,44 @@
+// @vitest-environment jsdom
+import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
+import {cleanup, fireEvent, render, screen, waitFor} from '@testing-library/react';
+import {MemoryRouter, Route, Routes} from 'react-router-dom';
+import GameDetail from './GameDetail.jsx';
+
+vi.mock('react-i18next', () => import('../test/i18n-mock.js'));
+vi.mock('sonner', () => ({toast: {success: vi.fn(), error: vi.fn()}}));
+
+const game = {
+    appid: 220, name: 'Half-Life 2', playtimeMinutes: 100, playtime2Weeks: 90, status: 'BACKLOG',
+    rating: null, notes: null, priority: null, hasAchievements: false, statsVisible: false, achievements: [],
+};
+
+const renderDetail = () => render(
+    <MemoryRouter initialEntries={['/library/220']}>
+        <Routes><Route path="/library/:appid" element={<GameDetail/>}/></Routes>
+    </MemoryRouter>,
+);
+
+beforeEach(() => {
+    localStorage.setItem('tbp_jwt', 'token');
+    globalThis.fetch = vi.fn(async (url, init) => init?.method === 'PUT'
+        ? {ok: true, status: 200, json: async () => JSON.parse(init.body)}
+        : {ok: true, status: 200, json: async () => game});
+});
+
+afterEach(() => {
+    cleanup();
+    localStorage.clear();
+});
+
+describe('GameDetail', () => {
+    it('keeps unsaved notes in the backlog card when the hint sets the game to playing', async () => {
+        renderDetail();
+        const notes = await screen.findByLabelText('BACKLOG.NOTES_LABEL');
+        fireEvent.change(notes, {target: {value: 'my draft'}});
+
+        fireEvent.click(screen.getByRole('button', {name: 'GAME_DETAIL.SET_PLAYING'}));
+
+        await waitFor(() => expect(screen.queryByRole('button', {name: 'GAME_DETAIL.SET_PLAYING'})).toBeNull());
+        expect(screen.getByLabelText('BACKLOG.NOTES_LABEL').value).toBe('my draft');
+    });
+});