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/index.html

@@ -102,7 +102,10 @@
         <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M6 16V11a6 6 0 0 1 12 0v5l1.5 2h-15z"/><path d="M10 20.5a2 2 0 0 0 4 0"/></svg>
         <span class="nav-label">Alerts</span>
       </a>
-      <a class="nav-link" href="/stats" data-section="stats" aria-label="Stats">
+      <!-- Secondary: full-width in the desktop sidebar, folded into the
+           "More" tab's sheet on the phone-width bottom bar instead (see
+           .nav-link-secondary in app.css and openNavMenu in app.js). -->
+      <a class="nav-link nav-link-secondary" href="/stats" data-section="stats" aria-label="Stats">
         <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M4 20h16M7 20v-7M12 20V6M17 20v-10"/></svg>
         <span class="nav-label">Stats</span>
       </a>
@@ -113,22 +116,26 @@
       <!-- Hidden unless the signed-in user is a system administrator; app.js
            unhides it once /api/me says so. The server refuses every admin
            endpoint regardless, so this is a courtesy and not a gate. -->
-      <a class="nav-link" href="/admin" data-section="admin" aria-label="Admin" id="nav-admin" hidden>
+      <a class="nav-link nav-link-secondary" href="/admin" data-section="admin" aria-label="Admin" id="nav-admin" hidden>
         <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M12 3l7 3v6c0 4-3 7-7 9-4-2-7-5-7-9V6z"/></svg>
         <span class="nav-label">Admin</span>
       </a>
-      <a class="nav-link" href="/more" data-section="more" aria-label="Account">
+      <a class="nav-link nav-link-secondary" href="/more" data-section="more" aria-label="Account">
         <svg viewBox="0 0 24 24" aria-hidden="true"><circle cx="12" cy="8" r="3.5"/><path d="M5 20a7 7 0 0 1 14 0"/></svg>
         <span class="nav-label">Account</span>
       </a>
+      <!-- Phone-width only (see .nav-more-btn in app.css): opens the same
+           sheet the old hamburger button did, for the sections the bottom
+           bar has no room for. Not shown on the desktop sidebar, which lists
+           every section already. -->
+      <button class="nav-link nav-more-btn" id="nav-more-btn" type="button" aria-label="More sections" aria-haspopup="menu">
+        <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M5 12h.01M12 12h.01M19 12h.01"/></svg>
+        <span class="nav-label">More</span>
+      </button>
     </nav>
 
     <header class="topbar">
       <div class="topbar-left">
-        <button class="btn btn-ghost btn-icon" id="menu-btn" type="button" aria-label="Menu" aria-haspopup="menu">
-          <svg viewBox="0 0 24 24" aria-hidden="true"><path d="M4 7h16M4 12h16M4 17h16"/></svg>
-          <span class="nav-badge menu-btn-badge" data-badge hidden></span>
-        </button>
         <button class="team-selector-mobile" id="team-selector-mobile" type="button" hidden></button>
         <h1 class="topbar-title" id="topbar-title">Queue</h1>
       </div>