Co-authored-by: DeepBlueV7.X <nicolas.werner@hotmail.de>

Fixes #1363

Please note that this doesn't prompt when you try to send a message with a bad command.

Since this causes crashes on some qml module updates.

Fixes #1383
Fixes #1132

fixes #1355

So far we haven't seen any reduction in issues about database
corruption, so presumably this is unrelated and the lag is annoying.

Instead of completing the list of Linux, Windows and the BSDs (NetBSD and
DragonFly would still be missing), simply flip it to not-macOS to simplify
and fix the two other aforementioned BSDs at once.

CMake builds ManagerLinux.cpp on `!MAC && !WIN`, that is BSD and Linux.
Fix the Linux-only assumption in the shared header.

Qt's `Q_OS_UNIX` is defined on Linux, BSDs and macOS alike.

See also:
https://daniel.haxx.se/blog/2023/01/08/copyright-without-years/
https://hynek.me/til/copyright-years/