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/PublicProfilePage.test.jsx

@@ -62,6 +62,18 @@ describe('PublicProfilePage', () => {
         }
     });
 
+    it('shows only the stat groups the user shares, without links', async () => {
+        library.stats = {pile: null, trend: null, topGames: null, taste: null, finished: null,
+            habits: {moonTrips: 2.5, longestDay: null, underOneHourGames: 0, underOneHourShare: null}};
+        mockBackends();
+        renderPage();
+
+        expect(await screen.findByText('STATS.HABITS.TITLE')).toBeTruthy();
+        expect(screen.queryByText('STATS.PILE.TITLE')).toBeNull();
+        expect(screen.queryByText('STATS.TOP_GAMES.TITLE')).toBeNull();
+        delete library.stats;
+    });
+
     it('says the profile is unknown or private on a 404', async () => {
         mockBackends({profileStatus: 404});
         renderPage();