Add a timeline page grouping photos by day

New /timeline/ page renders photos grouped into consecutive same-day
runs (ISO date heading plus per-day count), reusing the square grid.
groupByDay collapses the newest-first photo list; the page is not
paginated. Linked from the profile header.

static/style.css

@@ -187,6 +187,34 @@ body {
 .pager-newer { margin-right: auto; }
 .pager-older { margin-left: auto; }
 
+/* ── Timeline ──────────────────────────────────────────────── */
+
+.tl-day {
+  margin-bottom: 34px;
+}
+
+.tl-date {
+  display: flex;
+  align-items: baseline;
+  gap: 10px;
+  font-family: monospace;
+  font-size: 15px;
+  font-weight: 600;
+  color: var(--fg2);
+  letter-spacing: 0.04em;
+  padding: 0 3px 10px;
+  margin-bottom: 3px;
+  border-bottom: 1px solid var(--line);
+}
+
+.tl-count {
+  font-family: monospace;
+  font-size: 11px;
+  font-weight: 400;
+  color: var(--fg4);
+  letter-spacing: 0.04em;
+}
+
 /* ── Single photo page ─────────────────────────────────────── */
 
 .photo-page {