style: update padding for body and add early return in day detail function

- Adjusted the bottom padding in `style.css` to improve layout by incorporating a comfortable offset for safe areas.
- Added an early return in `dayDetail.js` to prevent further processing when there are no duties or event summaries, enhancing performance and preventing unnecessary DOM manipulations.

webapp/js/dayDetail.js

@@ -221,6 +221,8 @@ function openDayDetail(cell) {
   const duties = /** @type {object[]} */ (parseDataAttr(dutiesRaw || ""));
   const eventSummaries = /** @type {string[]} */ (parseDataAttr(eventsRaw || ""));
 
+  if (duties.length === 0 && eventSummaries.length === 0) return;
+
   ensurePanelInDom();
   if (!panelEl) return;