Add bilingual day-label headers with Latin weekday/season/ordinal vocabulary

Builds every day label as a {en, la} pair (weekdays, ranks, season/ordinal
phrasing authored in Latin; proper names without an authored Latin form
fall back to their English string) and merges the date+day-label into one
header in the day-nav bar.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/ui/hour-view.ts

@@ -149,7 +149,6 @@ export function renderHourView(container: HTMLElement): void {
   container.innerHTML = `
     <div class="hour-view">
       <h2>${hourLabel(selectedHour)}</h2>
-      ${ordo.dayLabel ? `<p class="day-label">${escapeHtml(ordo.dayLabel)}</p>` : ''}
       ${ordo.parts.map((part) => renderPart(part, languages)).join('')}
     </div>
   `;