Detach EquipmentBox event before programmatically setting equipment to
prevent async UpdateDrawingDropdownAsync from clearing the drawing
selection and duplicating entries. Also update ExportRecord.PdfContentHash
in StorePdfAsync so the web frontend can serve PDF downloads.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Add FileStorageService for DXF/PDF storage using content hashing,
FileStorageOptions config, FilesController for uploads, and
FileBrowserController for browsing stored files.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
