feat(android): say that work is happening, on every screen

The home screen's buttons already dimmed during an operation, but from the
list nothing moved: deleting or duplicating takes a second or two - the
container's round trip - and the screen stayed identical, as if the tap had
not registered. A veil with a turning arc now covers any screen, and it also
prevents the second tap, which would not wait any better.

Its safety net is the existing 25 s deadline: even if an operation never
hands back, the veil lifts.

The plan records where deleted entries actually are: every publish is a Gitea
commit, so the snapshot from before the deletion is still in the repository's
history, readable in its web interface and recoverable by import. Not a
screen, but a real net - and one that catches what a trash would not: an
unlucky edit, a bad import.

mainApk.pas

@@ -2295,6 +2295,9 @@ begin
   FBusy := ABusy;
   FDeadline.Enabled := False;   // reposee a zero, pas prolongee
   FDeadline.Enabled := ABusy;
+  // Les boutons de l'accueil palissaient deja, mais depuis la liste rien ne
+  // disait qu'on travaillait : le voile vaut pour tous les ecrans.
+  WebCall('PM.setBusy(' + LowerCase(BoolToStr(ABusy, True)) + ')');
   LCanOpen := HasVault and not FVaultUnreadable;
   // L'intitule suit l'etat du cache et non un mot fixe : sans coffre local,
   // l'action n'est pas une synchronisation mais un premier telechargement, et