Outsource custom GUI class components to dashgui library

Move reusable GUI primitives (PanelTile, EditablePanelTile, base Tile,
ElevatedPill, SingleLineTextEdit) into the shared dashgui package and
consume them via a file: dependency. EditablePanelTile now accepts an
onError prop so error notification stays app-side.

src/components/article/boxes/ArticleViewStock.jsx

@@ -1,7 +1,7 @@
 import { Component, PureComponent } from 'react';
 import Box from '@mui/material/Box';
 import Typography from '@mui/material/Typography';
-import { PanelTile } from '../../panels';
+import { PanelTile } from 'dashgui/panels';
 import { formatStock } from '../../../pages/artikel/searchFormat';
 
 class PanelValue extends Component {