Reading activity grid in Settings: months, weeks, days, hours with drill-down

Active reader time is now kept per user in small UTC buckets (6 minutes for
120 days, then hours, dropped after three years), seeded once from the visits
the clock still remembers. Settings -> Reading activity shows them as a grid
whose cells glow with their total and carry a start-to-end strip; month/week
cells open their days, days open their hours. Finished chapters come from
progress and work without the clock.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

test/services.test.js

@@ -148,6 +148,15 @@ test('three services integrate collections, auth, custom covers and private heal
     assert.equal((await send(visit(first, 'beacon-first', 2, { activeMs: 500, seen: [0], final: true, release: true }))).accepted, true);
     assert.equal((await send(visit(second, 'third-visit', 1))).accepted, false);
     await send(visit(second, 'second-visit', 2, { release: true }));
+    // The activity grid gets every credited millisecond once, duplicates and stale pulses excluded.
+    assert.equal((await request('/api/progress', { m: first.manga.id, c: first.chapter.id, v: first.version, p: 0, n: 1, done: true })).status, 200);
+    const activity = await (await request('/api/reading/activity')).json();
+    assert.equal(activity.readingClock, true);
+    assert.equal(activity.buckets.reduce((sum, b) => sum + b[2], 0), 2000);
+    assert.deepEqual(activity.mangas.map(m => m.id), [first.manga.id]);
+    assert.equal(activity.done.length, 1); assert.equal(activity.done[0][2], first.chapter.label);
+    assert.equal((await request('/api/reading/delete', { m: first.manga.id })).status, 200);
+    assert.equal((await (await request('/api/reading/activity')).json()).buckets.length, 0);
     assert.equal((await fetch(base + '/api/reading/visit', { method: 'POST', headers: { 'content-type': 'application/json' }, body: JSON.stringify(visit(first, 'unauth-visit', 1)) })).status, 401);
     await request('/api/settings', { readingClock: false });
     assert.equal((await request('/api/reading/visit', visit(first, 'disabled-visit', 1))).status, 403);