## Summary
Fix crash in kdeconnect-sms if a conversation contains a message which has no addresses.
I am not sure why this would happen and there's probably something which should be fixed on the Android side to ensure that every message has addresses, but this is an easy fix to prevent user-reported crashes.
BUG: 449719
## Test Plan
### Before:
kdeconnect-sms crashes upon selecting a conversation with a message with no addresses
### After:
kdeconnect-sms does not crash
- Move the device combobox to the global drawer
- Move search field and new button to header
- Use Kirigami SearchField instead
- Don't switch focus away from search field when typing
- Give the New button an icon
- Clarify the search field text
- Center messages view loading indicator
- Make send and attach buttons stick to bottom of text area
- Make cursor an I-beam when hovering over text area
- Move send button to the right
- Give proper padding to messages view top
- Move refresh action to global drawer
- Show refresh button directly in loading message where it is most useful
| Before | After |
| ------ | ------ |
|  |  |
|  |  |
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cc @teams/usability @teams/vdg
This commit makes use of the Kirigami.PlaceholderMessage component
instead of a QML Label, also moves the placeholder message to be
inside the ListView.
## Summary
Replace the (deprecated and removed) reference to `Kirigami.Theme.viewBackgroundColor` with `Kirigami.Theme.backgroundColor`
This element is necessary in order to have theme hot-switching work correctly
BUG 434791
## Test Plan
### Before:
When using the KDE Connect SMS app in an un-modified dark theme, the message entry text box would be rendered as all white and text would correctly be rendered in white (making it un-readable).
This seems to be somehow related to a recent Kirigami version (it only happened to me after doing a distro upgrade and my ancient Kirigami installed to ~/.prefix does not reproduce the issue).
viewBackgroundColor was deprecated and apparently removed from Kirigami a version or two ago. Thus the coloring was no longer correct.
For screenshots and discussion, see [bug 434791](https://bugs.kde.org/show_bug.cgi?id=434791)
### After:
Text and background are rendered in the expected colours for the theme.
On Plasma qqc2-desktop-style is used automatically, but not on other
DEs. Set it as a default and allow overriding it via environment
variables.
Also add it as a runtime dep so distros actually ship it.
We use kdeconnect-version.h in several places and therefore it needs to be in the include path. We currently do this by setting target_include_path in a few places. Replace this with an interface library that we can link against that sets up the correct include path. IMO it is cleaner this way.
Turn smshelper into a static library, which makes sense given it's only used internally at this point. This allows to get rid of some stuff.
Also cleanup other things.
While mostly theoretical it makes for a more expressive API since it communicates that it is a list instead of a single value. It also allows to get rid of some conversion code.
This is also preparation work for potentially using the custom type capabilities that QtDBus offers.
