Release v2.19.4 (#259)

Release v2.19.4.

**Fixed**
- A deleted occurrence stays deleted through a series re-timing, and through backup/restore ([#225]).
- "Only this event" saves the edit on calendars that never synced, and on a row that doesn't recur it edits or deletes the event itself instead of filing an exception against nothing.
- A reminder left on the account's default is no longer read as a lead time of Calendula's own.
- The widgets turn the page at midnight; the re-arm backstop for the inexact rollover alarm is back, throttled to once per 15 minutes on calendar changes.
- An event running past midnight can be dragged by either half ([#253]).
- One event the provider refuses no longer costs the rest of the import, and an import cut short reports honestly how far it got.
- EXDATE zone prefixes are read in the bare `<zone>;` form the provider and DAVx5 actually write, not only the iCalendar `TZID=` spelling; a list holding a stamp we can't parse is kept whole rather than re-emitted stripped of its zone; RDATE travels with RRULE when the recurrence set is rewritten.

**Added**
- Belarusian, Hungarian and Slovak, from community translators on Weblate.

**Changed**
- Arabic, Polish and Simplified Chinese are complete; Czech grew, and Russian is now at about half.

Bumps `versionName` to 2.19.4, so merging this triggers the release pipeline.

Co-authored-by: Jean-Luc Makiola <business@jeanlucmakiola.de>
Reviewed-on: https://codeberg.org/jlmakiola/calendula/pulls/259

app/src/main/res/xml/locales_config.xml

@@ -10,14 +10,17 @@
 <locale-config xmlns:android="http://schemas.android.com/apk/res/android">
     <locale android:name="en" />
     <locale android:name="ar" />
+    <locale android:name="be" />
     <locale android:name="cs" />
     <locale android:name="de" />
     <locale android:name="es" />
     <locale android:name="fr" />
+    <locale android:name="hu" />
     <locale android:name="it" />
     <locale android:name="ja" />
     <locale android:name="pl" />
     <locale android:name="pt-BR" />
     <locale android:name="ru" />
+    <locale android:name="sk" />
     <locale android:name="zh-CN" />
 </locale-config>