feat(stats): add stats page and pile trend

Show the stat groups on /stats, the pile trend on the dashboard card,
one switch per group in the settings, and the shared groups on the
public profile.

src/pages/StatsPage.test.jsx

@@ -0,0 +1,87 @@
+// @vitest-environment jsdom
+import {afterEach, beforeEach, describe, expect, it, vi} from 'vitest';
+import {cleanup, fireEvent, render, screen, waitFor} from '@testing-library/react';
+import {MemoryRouter} from 'react-router-dom';
+import StatsPage from './StatsPage.jsx';
+import {PreferencesProvider} from '../context/PreferencesContext.jsx';
+
+vi.mock('react-i18next', () => import('../test/i18n-mock.js'));
+
+const json = (body, status = 200) => ({ok: status < 400, status, json: async () => body});
+
+const stats = (extra = {}) => ({
+    overview: {totalGames: 12, totalPlaytimeMinutes: 6000, playedGames: 8, neverStarted: 4,
+        byStatus: {BACKLOG: 5, PLAYING: 3, FINISHED: 2, COMPLETED: 1, DROPPED: 1}},
+    pile: {backlogGames: 5, normalMinutes: 4200, completionistMinutes: 9000, gamesWithTimeToBeat: 4,
+        minutesPerWeek: 420, paceWeeks: 10, workYears: 0.03,
+        oldestUnplayed: {appid: 220, name: 'Half-Life 2', imageUrl: null, inLibrarySince: '2026-01-01T00:00:00Z'}},
+    topGames: {mostPlayed: [{appid: 620, name: 'Portal 2', imageUrl: null, minutes: 900}],
+        mostLoyal: {appid: 620, name: 'Portal 2', imageUrl: null, months: 3, minutes: 900}},
+    taste: {genres: [{name: 'Shooter', games: 2, minutes: 1200}], moods: [{name: 'CHILL', games: 1, minutes: 900}]},
+    habits: {moonTrips: 0.5, longestDay: {day: '2026-07-01', minutes: 200}, underOneHourGames: 1, underOneHourShare: 0.125},
+    finished: {perYear: [{year: 2026, games: 2}], finishedBeforeTracking: 1},
+    trend: {days: [{day: '2026-09-26', backlogGames: 6, neverPlayed: 4, backlogMinutes: 5000},
+        {day: '2026-09-27', backlogGames: 5, neverPlayed: 4, backlogMinutes: 4200}], thisMonth: {added: 1, done: 2}},
+    ...extra,
+});
+
+const renderPage = () => render(<MemoryRouter><PreferencesProvider><StatsPage/></PreferencesProvider></MemoryRouter>);
+
+describe('StatsPage', () => {
+    beforeEach(() => {
+        localStorage.setItem('tbp_session', '1');
+    });
+
+    afterEach(() => {
+        cleanup();
+        localStorage.clear();
+    });
+
+    it('asks for every group once and shows each of them', async () => {
+        globalThis.fetch = vi.fn(async () => json(stats()));
+        renderPage();
+
+        expect(await screen.findByText('STATS.OVERVIEW.TITLE')).toBeTruthy();
+        expect(fetch).toHaveBeenCalledOnce();
+        expect(fetch.mock.calls[0][0]).toMatch(/\/api\/library\/stats$/);
+        for (const title of ['PILE', 'TREND', 'TOP_GAMES', 'TASTE', 'HABITS', 'FINISHED']) {
+            expect(screen.getByText(`STATS.${title}.TITLE`)).toBeTruthy();
+        }
+        expect(screen.getAllByText('Portal 2')).toHaveLength(2);
+        expect(screen.getByText('Half-Life 2')).toBeTruthy();
+        expect(screen.getByText('STATS.PILE.PACE')).toBeTruthy();
+        expect(screen.getByText('STATS.FINISHED.BEFORE:1')).toBeTruthy();
+        expect(screen.getByTestId('pile-trend')).toBeTruthy();
+    });
+
+    it('shows the empty texts of a new library', async () => {
+        const empty = stats();
+        globalThis.fetch = vi.fn(async () => json({
+            ...empty,
+            pile: {...empty.pile, paceWeeks: null, oldestUnplayed: null},
+            topGames: {mostPlayed: [], mostLoyal: null},
+            taste: {genres: [], moods: []},
+            habits: {moonTrips: 0, longestDay: null, underOneHourGames: 0, underOneHourShare: null},
+            finished: {perYear: [], finishedBeforeTracking: 0},
+            trend: {days: [empty.trend.days[1]], thisMonth: {added: 0, done: 0}},
+        }));
+        renderPage();
+
+        expect(await screen.findByText('STATS.PILE.PACE_NONE')).toBeTruthy();
+        expect(screen.getByText('STATS.TOP_GAMES.EMPTY')).toBeTruthy();
+        expect(screen.getByText('STATS.TASTE.EMPTY')).toBeTruthy();
+        expect(screen.getByText('STATS.FINISHED.EMPTY')).toBeTruthy();
+        expect(screen.getByText('STATS.TREND.STARTS')).toBeTruthy();
+        expect(screen.queryByText('STATS.HABITS.LONGEST_DAY')).toBeNull();
+        expect(screen.queryByTestId('pile-trend')).toBeNull();
+    });
+
+    it('offers a retry when the stats could not be loaded', async () => {
+        globalThis.fetch = vi.fn(async () => json({}, 500));
+        renderPage();
+
+        fireEvent.click(await screen.findByRole('button', {name: /DASHBOARD.RETRY/}));
+
+        await waitFor(() => expect(fetch).toHaveBeenCalledTimes(2));
+    });
+});