feat(ui): add auto-refresh after upload and inline file preview

- Auto-refresh files table after successful uploads using custom event
- Add inline preview support for PDFs, images, and text files
- Set Content-Disposition header to inline for preview endpoint
- Add download button as secondary action in file details view

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/api/files.py

@@ -568,7 +568,7 @@ def get_file_preview(
         return FileResponse(
             path=file_path,
             media_type=file_record.mime_type or "application/pdf",
-            filename=file_record.original_filename,
+            headers={"Content-Disposition": f'inline; filename="{file_record.original_filename}"'},
         )
 
     except HTTPException: