fix: T4a browser check findings

- Withdrawal wording from one backend helper everywhere ("bis
  einschließlich TT.MM. – ab TT.MM. wieder erntefähig", year when it
  crosses New Year); withdrawal-status returns lastBlockedDay and the
  ready text, the frontend no longer computes dates
- Calendar events name colony or apiary, withdrawal events carry
  product and detail; compact withdrawal rows on mobile
- One bottling warning per colony and treatment; pre-save hint
- Offline: online-only actions disabled with a reason, cached data
  shows its timestamp, open sheets block submit offline
- Mobile: no horizontal scroll at 360 px, touch targets >= 44 px,
  toasts and the add button no longer cover content
- Cleanup sheet without destructive preselection; natural sort of
  colony codes; collapsible automation rule cards; varroa list newest
  first with chart axes; text fixes

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

ApiCore-Backend/src/common/format-day.ts

@@ -0,0 +1,13 @@
+/** '2026-05-05' as '05.05.', with the year as '05.05.2026'. */
+export function formatDayDe(day: string, withYear = false): string {
+  const [year, month, date] = day.split('-');
+  return withYear ? `${date}.${month}.${year}` : `${date}.${month}.`;
+}
+
+/**
+ * Closes a sentence with one period. A day formatted by formatDayDe ends with
+ * its own dot ('13.10.'), which then is the end of the sentence.
+ */
+export function endSentence(text: string): string {
+  return text.endsWith('.') ? text : `${text}.`;
+}