Set initial focus on the search bar on startup

BUG: 427077

app/kiten.cpp

@@ -299,7 +299,7 @@ void Kiten::finishInit()
     }
   }
 
-//   Edit->Completion()->clear(); // make sure the edit is focused initially
+  _inputManager->focusInput();
   _statusBar->showMessage( i18n( "Welcome to Kiten" ) );
   setCaption( QString() );
 }

app/searchstringinput.h

@@ -46,13 +46,11 @@ class SearchStringInput : public QObject
 
   public slots:
     void      test();
+    void      focusInput();
 
   signals:
     void      search();
 
-  private slots:
-    void      focusInput();
-
   private:
     KSelectAction    *_actionFilterRare = nullptr;
     // Search exact/anywhere/beginning