Stats: heatmap to GitHub scale (365 days + month labels)

- heatmap now fetches /api/stats?days=365 (endpoint already caps at
  365; no server change) so the grid spans the past year
- week columns with month labels (Aug, Sep, ...), first column
  labelled by its first in-window day, final column padded
- grid wrapped in a horizontal-scroll container (53 weeks ~ 750px)

static/style.css

@@ -56,7 +56,11 @@ h2 { margin: 0.4rem 0; }
 .grid.stats { grid-template-columns: repeat(auto-fit, minmax(150px, 1fr)); }
 .card.stat { padding: .8rem; gap: .2rem; }
 .stat-value { font-size: 1.3rem; font-weight: 700; }
-.heat { display: grid; grid-auto-flow: column; grid-template-rows: repeat(7, 11px); gap: 3px; width: fit-content; margin: .5rem 0 .3rem; }
+.heat-wrap { overflow-x: auto; margin: .5rem 0 .3rem; }
+.heat-lbl { display: flex; gap: 3px; margin-bottom: 2px; }
+.heat-lbl .heat-lab { width: 14px; font-size: .65rem; color: var(--muted); white-space: nowrap; }
+.heat { display: flex; gap: 3px; }
+.heat-col { display: flex; flex-direction: column; gap: 3px; }
 .heat i, .heat-lg i { width: 11px; height: 11px; border-radius: 2px; background: var(--bd); }
 .heat i.none { background: transparent; }
 .heat i.l1, .heat-lg i.l1 { background: color-mix(in srgb, var(--acc) 30%, var(--bd)); }