fix: no icon under Windows

See also:

- https://invent.kde.org/frameworks/kiconthemes/-/issues/3
- https://planet.kde.org/christoph-cullmann-2024-05-11-kde-applications-icons/

(cherry picked from commit 82434fe87c)

src/CMakeLists.txt

@@ -418,6 +418,7 @@ target_link_libraries(neochat PUBLIC
     KF6::ConfigGui
     KF6::CoreAddons
     KF6::SonnetCore
+    KF6::IconThemes
     KF6::ColorScheme
     KF6::ItemModels
     QuotientQt6

src/main.cpp

@@ -37,6 +37,7 @@
 #include <KCrash>
 #endif
 
+#include <KIconTheme>
 #include <KLocalizedContext>
 #include <KLocalizedString>
 
@@ -101,6 +102,7 @@ Q_DECL_EXPORT
 #endif
 int main(int argc, char *argv[])
 {
+    KIconTheme::initTheme();
     QNetworkProxyFactory::setUseSystemConfiguration(true);
 
 #ifdef HAVE_WEBVIEW