feat(delivery): add supplier article lookup, article creation, and unified parsing

- Unified PDF/TXT parsing to single POST /api/delivery/parse endpoint
- Added supplier article lookup with SKU/EAN matching in delivery lines
- Added "Artikel anlegen" button to create articles from missing SKUs
- Fixed delivery line taxrate field (was sending 'tax', now 'taxrate')
- Extended TXT file support for rescan functionality
- Updated ApiClient with getArticles method for supplier article lookup
- Added supplier article state management to deliveryEditorAutomat

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src/components/manifest/Attachment.jsx

@@ -163,7 +163,7 @@ export class Attachment extends PureComponent {
           }}
           onClick={(e) => e.stopPropagation()}
         >
-          {isPdf ? (
+          {isPdf || isText ? (
             <Tooltip title="Neu analysieren">
               <span>
                 <IconButton