Web: visual design pass (issue #26)

Addresses the screenshot-review feedback in #26. No framework or build
step added — all of this stays within the existing plain HTML/CSS/
vanilla-JS + go:embed architecture.

- Nav: re-enable the bottom tab bar that was already built and
  switched off (Queue/On-call/Alerts/Team + a "More" sheet for
  Stats/Admin/Account), replacing the hamburger on phone width.
- Queue: chip counts, a scroll fade on the filter row, a
  "Triggered Xh ago" + severity label per row, a chevron on the team
  switcher so it reads as a dropdown.
- On-call: collapse repeated same-person days into shift bars (week
  view and "your shifts" both), show the week as a date range with
  the ISO week number as secondary text, split "Current shift" out
  from "Next shifts" with "ends in Nd", a pill badge + row highlight
  for "you".
- Incident detail: fix the actual bug behind the duplicate
  "acknowledged" timeline entries (acknowledgeIncident's UPDATE had no
  guard on the incident's current status, so acknowledging an
  already-acknowledged incident silently re-logged the event — now
  idempotent, with regression tests on both the authenticated route
  and the ntfy ack-button route). Relabel escalation re-pages so they
  don't look like the same page landing twice. Copy the primary action
  up near the top. Label the "···" button. Group the timeline by
  phase (triggered/acknowledged/resolved). Add an "at a glance"
  summary row (duration/severity/responsible) and collapse the group
  labels by default.
- Team overview: reword the vague copy ("One owner." etc.) into plain
  labels.
- Empty states: fill in missing icons/one-liners across queue,
  alerts, stats and the incident timeline.
- CSS: fix card padding bugs, verify link contrast already passes AA,
  introduce a --fs-* type-scale token set and migrate the few
  genuinely isolated cases onto it (left sizes tied to a fixed shape,
  a deliberately prominent display, or a non-negotiable constraint
  like the iOS-zoom-prevention input size as documented exceptions
  rather than guess at a render this change can't see).

Verified with the full fmt/lint/test/helm-lint gate, plus a live
instance against the test DB with seeded incidents and schedule data
to trace the on-call grouping and timeline phase-splitting logic
against real API responses.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

internal/web/static/js/ui.js

@@ -52,6 +52,7 @@ const ICONS = {
   trash: ['M4 7h16', 'M9 7V4h6v3', 'M6 7l1 13h10l1-13'],
   chevronLeft: ['M15 18l-6-6 6-6'],
   chevronRight: ['M9 6l6 6-6 6'],
+  chevronDown: ['M6 9l6 6 6-6'],
   external: ['M14 4h6v6', 'M20 4l-9 9', 'M18 14v6H4V6h6'],
   logout: ['M15 4h4v16h-4', 'M10 17l5-5-5-5', 'M15 12H4'],
 };
@@ -186,12 +187,16 @@ export function labelChip(k, v) {
 // One entry in a section's overview: a card that is a link, carrying the count
 // only that section can state. Both the Admin tab and the Team tab open on one
 // of these menus, and a menu item is a shape rather than a page's own idea.
+// note is usually just a string, but can be an array of children instead —
+// deadman's "healthy" note below pairs text with a status icon.
 export function menuCard(href, label, count, note) {
   return h('a', { class: 'card overview-item', href },
     h('div', { class: 'overview-head' },
       h('strong', { text: label }),
       count != null && h('span', { class: 'overview-count', text: String(count) })),
-    h('p', { class: 'muted small', text: note }),
+    typeof note === 'string'
+      ? h('p', { class: 'muted small', text: note })
+      : h('p', { class: 'muted small' }, note),
   );
 }