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/components/PileOfShameCard.test.jsx

@@ -42,6 +42,21 @@ describe('PileOfShameCard', () => {
         expect(onShuffle).toHaveBeenCalledOnce();
     });
 
+    it('shows the pile trend and the moves of this month once they are loaded', () => {
+        const trend = {days: [{day: '2026-09-26', backlogGames: 3}, {day: '2026-09-27', backlogGames: 2}],
+            thisMonth: {added: 1, done: 2}};
+        renderCard({summary: summary(2), trend});
+
+        expect(screen.getByText('STATS.TREND.THIS_MONTH')).toBeTruthy();
+        expect(screen.getByTestId('pile-trend')).toBeTruthy();
+    });
+
+    it('shows no trend while it is not loaded', () => {
+        renderCard({summary: summary(2)});
+
+        expect(screen.queryByText('STATS.TREND.THIS_MONTH')).toBeNull();
+    });
+
     it('says the backlog is empty when there is no suggestion', () => {
         renderCard({summary: summary(0)});