Add 'CenterOnCursor' command and improve cursor scrolling logic

- Introduced `CommandId::CenterOnCursor` to center viewport on the cursor line.
- Improved scrolling behavior in `ImGuiRenderer` to avoid aggressive centering and keep visible lines stable.
- Updated `make-app-release` to rename the output app to `kge-qt.app`.
- Adjusted padding in `ImGuiFrontend` to align with `ImGuiRenderer` settings for consistent scrolling.
- Bumped version to 1.4.1.

KKeymap.cc

@@ -42,6 +42,9 @@ KLookupKCommand(const int ascii_key, const bool ctrl, CommandId &out) -> bool
 	case 'a':
 		out = CommandId::MarkAllAndJumpEnd;
 		return true;
+	case 'k':
+		out = CommandId::CenterOnCursor; // C-k k center current line
+		return true;
 	case 'b':
 		out = CommandId::BufferSwitchStart;
 		return true;
@@ -215,4 +218,4 @@ KLookupEscCommand(const int ascii_key, CommandId &out) -> bool
 		break;
 	}
 	return false;
-}
+}