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/AndroidManifest.xml

@@ -330,9 +330,13 @@
         </receiver>
 
         <!-- Keeps both widgets fresh: the calendar provider broadcasts
-             PROVIDER_CHANGED on any data change (our writes and external sync),
-             and the system broadcasts the date/time ones at midnight / clock
-             changes so "today" highlighting rolls over. -->
+             PROVIDER_CHANGED on any data change (our writes and external sync).
+             The day boundary arrives as the app's own ROLLOVER alarm (#228), by
+             explicit PendingIntent, so it needs no filter here; DATE_CHANGED is
+             a free extra only, since Android 8+ withholds it from manifest
+             receivers. The four below re-arm that alarm: TIME_SET /
+             TIMEZONE_CHANGED move the boundary, boot / package-replace wipe it.
+             Exported: the system broadcasts arrive from outside the app. -->
         <receiver
             android:name=".widget.WidgetUpdateReceiver"
             android:exported="true">
@@ -346,6 +350,8 @@
                 <action android:name="android.intent.action.DATE_CHANGED" />
                 <action android:name="android.intent.action.TIME_SET" />
                 <action android:name="android.intent.action.TIMEZONE_CHANGED" />
+                <action android:name="android.intent.action.BOOT_COMPLETED" />
+                <action android:name="android.intent.action.MY_PACKAGE_REPLACED" />
             </intent-filter>
         </receiver>