feat: move revision tracking to ExportRecord, add perceptual hash comparison, cut list modal, and auto-start API

- Move Revision from Drawing to ExportRecord so each export captures its own revision snapshot
- Add Hamming distance comparison for perceptual hashes (tolerance of 10 bits) to avoid false revision bumps
- Replace CoenM.ImageHash with inline DifferenceHash impl (compatible with ImageSharp 3.x)
- Increase PDF render DPI from 72 to 150 for better hash fidelity
- Add download-dxfs-by-drawing endpoint for cross-export DXF zip downloads
- Prefix DXF filenames with equipment number when no drawing number is present
- Pass original filename to storage service for standalone part exports
- Auto-start FabWorks.Api from ExportDXF client if not already running
- Add cut list modal with copy-to-clipboard in the web UI
- Update PDF hash on existing export records after upload
- Bump static asset cache versions to v3

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

FabWorks.Api/Controllers/FilesController.cs

@@ -30,7 +30,7 @@ namespace FabWorks.Api.Controllers
                 return BadRequest("No file uploaded.");
 
             using var stream = file.OpenReadStream();
-            var result = await _fileStorage.StoreDxfAsync(stream, equipment, drawingNo, itemNo, contentHash);
+            var result = await _fileStorage.StoreDxfAsync(stream, equipment, drawingNo, itemNo, contentHash, file.FileName);
 
             return Ok(new FileUploadResponse
             {