[pending-judge] feat(DC-168): calendar widget UX + theming — "No upcoming appointments" state, month grid with highlighted appointment days, theme-correct styling

Owner directives (2026-10-10/11, verbatim in brief): show "no upcoming
appointments" when empty; show a month calendar with days and times
highlighted when there are events; stylize to fit every theme; keep the
widget weather-widget-sized.

Changes (status/ frontend + tests):
- status/js/calendar-widget.js: rewritten render path — chip states ("No
  upcoming appointments" / next appointment with highlighted when-span),
  month grid modal (cal-grid + prev/next nav, appointment days highlighted,
  per-event time dots), upcoming list with day/time emphasis, month-following
  fetch with window-authoritative event merge (via calendar-cache.js),
  forced refresh on periodic tick + source mutations, local escapeHtml (was
  an undefined global).
- status/js/calendar-cache.js (new): uid+start-keyed event cache; fetched
  window is authoritative for entries starting inside it (deletions and
  reschedules propagate), entries outside survive. Dual export (module +
  window) for tests and browser bundle.
- status/build.js: calendar-cache.js bundled before calendar-widget.js.
- status/css/dashboard.css: DC-168 block — chip states, month grid, day
  highlight states, dots, list/source rows, universal light-bg contrast
  rules (color-mix; WCAG >= 4.5:1 verified for all 10 builtin themes, worst
  4.60:1 ocean) + light-surface rules.

Tests: 20 total in __tests__/calendar — 9 in caldav-default-ns (extraction
incl. mixed docs, empty multistatus, namespace-aware fixture validation,
undeclared-prefix rejection both quote styles, positive declared-attr),
5 in dc168-cache-contract (merge, duplicate suppression, recurring uid+start,
window-authoritative removal on refetch, cross-window survival, ended-
exclusion), 6 in dc168-widget-contract (navigation fetch windows, forced-
refresh semantics, cache+widget integration, interval coverage). Existing
suites pass unmodified; eslint 0 errors on touched files.

status/build.js

@@ -81,6 +81,9 @@ const bundles = {
     JS('deploys.js'),
     JS('weather.js'),
     JS('clock.js'),
+    // DC-168: calendar event-cache semantics (uid+start keys, window-
+    // authoritative merge) — must precede calendar-widget.js.
+    JS('calendar-cache.js'),
     // DC-161: calendar widget — top-bar display + sources modal. Reads
     // /api/v1/calendar/*; auto-shows Radicale calendars deployed via DashCaddy.
     JS('calendar-widget.js'),