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.
- Edit toggle behind the "Kategorien" title enables an edit mode.
- In edit mode all category tiles become inline rename fields (no outline,
distinct background, small margins); articles and "new article" are hidden.
- Rename via PATCH /api/category/:id; reorder via PUT /api/category/order
(parentId + categoryIds) with SortableJS.
- Only call backend when order actually changed; revert DOM order on error
so further dragging keeps working.
- Redux: renameCategory + reorderCategories thunks, renameMode state.
