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/wwwroot/index.html

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-    <script src="js/icons.js?v=2"></script>
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-    <script src="js/components.js?v=2"></script>
-    <script src="js/pages.js?v=2"></script>
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+    <script src="js/icons.js?v=3"></script>
+    <script src="js/helpers.js?v=3"></script>
+    <script src="js/components.js?v=3"></script>
+    <script src="js/pages.js?v=3"></script>
+    <script src="js/router.js?v=3"></script>
     <script>router.init();</script>
 </body>
 </html>