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/ExportsController.cs

@@ -1,4 +1,6 @@
+using System.Globalization;
 using System.IO.Compression;
+using System.Numerics;
 using FabWorks.Api.DTOs;
 using FabWorks.Api.Services;
 using FabWorks.Core.Data;
@@ -215,8 +217,9 @@ namespace FabWorks.Api.Controllers
 
             if (!string.IsNullOrEmpty(record.DrawingNumber) && !string.IsNullOrEmpty(request.PdfContentHash))
             {
-                var drawing = await ResolveDrawingAsync(record.DrawingNumber, record.Title, request.PdfContentHash);
-                record.DrawingId = drawing.Id;
+                var (drawing, revision) = await ResolveDrawingAsync(record.DrawingNumber, record.Title, request.PdfContentHash);
+                record.Drawing = drawing;
+                record.DrawingRevision = revision;
             }
 
             await _db.SaveChangesAsync();
@@ -224,36 +227,42 @@ namespace FabWorks.Api.Controllers
             return NoContent();
         }
 
-        private async Task<Drawing> ResolveDrawingAsync(string drawingNumber, string title, string pdfContentHash)
+        private async Task<(Drawing drawing, int revision)> ResolveDrawingAsync(string drawingNumber, string title, string pdfContentHash)
         {
             var drawing = await _db.Drawings
                 .FirstOrDefaultAsync(d => d.DrawingNumber == drawingNumber);
 
+            // Get the highest revision recorded for this drawing across all exports
+            var lastRevision = await _db.ExportRecords
+                .Where(r => r.DrawingNumber == drawingNumber && r.DrawingRevision != null)
+                .OrderByDescending(r => r.DrawingRevision)
+                .Select(r => r.DrawingRevision)
+                .FirstOrDefaultAsync() ?? 0;
+
             if (drawing == null)
             {
                 drawing = new Drawing
                 {
                     DrawingNumber = drawingNumber,
                     Title = title,
-                    PdfContentHash = pdfContentHash,
-                    Revision = 1
+                    PdfContentHash = pdfContentHash
                 };
                 _db.Drawings.Add(drawing);
-            }
-            else if (drawing.PdfContentHash != pdfContentHash)
-            {
-                drawing.PdfContentHash = pdfContentHash;
-                drawing.Revision++;
-                if (!string.IsNullOrEmpty(title))
-                    drawing.Title = title;
-            }
-            // If hash matches, keep same revision (just update title if needed)
-            else if (!string.IsNullOrEmpty(title))
-            {
-                drawing.Title = title;
+                return (drawing, 1);
             }
 
-            return drawing;
+            if (!string.IsNullOrEmpty(title))
+                drawing.Title = title;
+
+            if (ArePerceptualHashesSimilar(drawing.PdfContentHash, pdfContentHash))
+            {
+                // Hash unchanged — keep same revision
+                return (drawing, lastRevision == 0 ? 1 : lastRevision);
+            }
+
+            // Hash changed — bump revision and update stored hash
+            drawing.PdfContentHash = pdfContentHash;
+            return (drawing, lastRevision + 1);
         }
 
         [HttpGet("previous-cut-template")]
@@ -316,6 +325,37 @@ namespace FabWorks.Api.Controllers
 
             if (dxfItems.Count == 0) return NotFound("No DXF files for this export.");
 
+            var zipName = $"{record.DrawingNumber ?? $"Export-{id}"} DXFs.zip";
+            return BuildDxfZip(dxfItems, zipName);
+        }
+
+        [HttpGet("download-dxfs")]
+        public async Task<IActionResult> DownloadDxfsByDrawing([FromQuery] string drawingNumber)
+        {
+            if (string.IsNullOrEmpty(drawingNumber))
+                return BadRequest("drawingNumber is required.");
+
+            var dxfItems = await _db.BomItems
+                .Include(b => b.CutTemplate)
+                .Where(b => b.ExportRecord.DrawingNumber == drawingNumber
+                         && b.CutTemplate != null
+                         && b.CutTemplate.ContentHash != null)
+                .ToListAsync();
+
+            if (dxfItems.Count == 0) return NotFound("No DXF files for this drawing.");
+
+            // Deduplicate by content hash (keep latest)
+            dxfItems = dxfItems
+                .GroupBy(b => b.CutTemplate.ContentHash)
+                .Select(g => g.Last())
+                .ToList();
+
+            var zipName = $"{drawingNumber} DXFs.zip";
+            return BuildDxfZip(dxfItems, zipName);
+        }
+
+        private FileResult BuildDxfZip(List<BomItem> dxfItems, string zipName)
+        {
             var ms = new MemoryStream();
             using (var zip = new ZipArchive(ms, ZipArchiveMode.Create, leaveOpen: true))
             {
@@ -341,16 +381,41 @@ namespace FabWorks.Api.Controllers
 
                     var entry = zip.CreateEntry(fileName, CompressionLevel.Fastest);
                     using var entryStream = entry.Open();
-                    await blobStream.CopyToAsync(entryStream);
+                    blobStream.CopyTo(entryStream);
                     blobStream.Dispose();
                 }
             }
 
             ms.Position = 0;
-            var zipName = $"{record.DrawingNumber ?? $"Export-{id}"} DXFs.zip";
             return File(ms, "application/zip", zipName);
         }
 
+        /// <summary>
+        /// Compares two perceptual hashes using Hamming distance.
+        /// Perceptual hashes (16 hex chars / 64 bits) are compared with a tolerance
+        /// of up to 10 differing bits (~84% similarity). SHA256 fallback hashes
+        /// (64 hex chars) use exact comparison.
+        /// </summary>
+        private static bool ArePerceptualHashesSimilar(string hash1, string hash2)
+        {
+            if (hash1 == hash2) return true;
+            if (string.IsNullOrEmpty(hash1) || string.IsNullOrEmpty(hash2)) return false;
+
+            // Perceptual hashes are 16 hex chars (64-bit DifferenceHash)
+            // SHA256 fallback hashes are 64 hex chars — require exact match
+            if (hash1.Length != 16 || hash2.Length != 16)
+                return false;
+
+            if (ulong.TryParse(hash1, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var h1) &&
+                ulong.TryParse(hash2, NumberStyles.HexNumber, CultureInfo.InvariantCulture, out var h2))
+            {
+                var hammingDistance = BitOperations.PopCount(h1 ^ h2);
+                return hammingDistance <= 10;
+            }
+
+            return false;
+        }
+
         private static ExportDetailDto MapToDto(ExportRecord r) => new()
         {
             Id = r.Id,

FabWorks.Api/Controllers/FileBrowserController.cs

@@ -88,7 +88,7 @@ namespace FabWorks.Api.Controllers
                         r.DrawingNumber,
                         r.PdfContentHash,
                         r.ExportedAt,
-                        DrawingRevision = r.Drawing != null ? (int?)r.Drawing.Revision : null
+                        r.DrawingRevision
                     });
 
                 if (!string.IsNullOrWhiteSpace(search))

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
             {