feat(documents): migrate storage to filesystem, add server-side pagination

- Replace Base64 data URIs with file-based storage served via dedicated endpoints
- Add DocumentPreviewModal navigation, DocumentThumbnail fileUrl support
- Refactor documents page with server-side pagination, search, sort and filters
- Update all components to use fileUrl/downloadUrl instead of raw path
- Add pagination composable support (total, page, itemsPerPage, attachmentFilter)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/pages/machine/[id].vue

@@ -10,6 +10,7 @@
       <DocumentPreviewModal
         :document="d.previewDocument.value"
         :visible="d.previewVisible.value"
+        :documents="d.machineDocumentsList.value"
         @close="d.closePreview"
       />