Fix F-Droid bot feedback issues [skip ci]

- Move fastlane metadata to repository root (was in android/fastlane)
- Add distributionSha256Sum to gradle-wrapper.properties for security
- Update Gradle Wrapper JAR to match version 8.13
- Document NonFreeNet anti-feature (HTTP support for local WebDAV servers)

Addresses F-Droid RFP issue #3458 bot feedback

fastlane/metadata/android/de-DE/changelogs/1.txt

@@ -0,0 +1,8 @@
+• Material Design 3 mit Dynamic Colors
+• Swipe-to-Delete mit Bestätigungsdialog
+• Server Backup & Restore Funktion
+• Verbesserte Empty State Ansicht
+• Deutsche Lokalisierung
+• Splash Screen Support (Android 12+)
+• Performance-Verbesserungen
+• Bug-Fixes