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/css/styles.css

@@ -735,6 +735,85 @@ tbody tr:last-child td { border-bottom: none; }
 .equip-group.collapsed .equip-body { display: none; }
 .equip-group.collapsed .equip-header { border-radius: 6px; }
 
+/* ─── Modal ─── */
+.modal-overlay {
+    position: fixed;
+    inset: 0;
+    background: rgba(0, 0, 0, 0.35);
+    backdrop-filter: blur(4px);
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    z-index: 200;
+    animation: fadeIn 0.15s ease;
+}
+
+@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
+
+.modal-panel {
+    background: var(--surface);
+    border: 1px solid var(--border);
+    border-radius: 8px;
+    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.15);
+    width: 90%;
+    max-width: 640px;
+    max-height: 80vh;
+    display: flex;
+    flex-direction: column;
+    animation: fadeSlideIn 0.2s ease forwards;
+}
+
+.modal-header {
+    padding: 14px 18px;
+    border-bottom: 1px solid var(--border-subtle);
+    font-family: var(--font-display);
+    font-weight: 600;
+    font-size: 14px;
+    letter-spacing: 0.02em;
+    display: flex;
+    align-items: center;
+    gap: 10px;
+    text-transform: uppercase;
+    color: var(--text-secondary);
+}
+
+.modal-header svg { width: 16px; height: 16px; }
+
+.modal-body {
+    overflow-y: auto;
+    flex: 1;
+}
+
+.btn-green {
+    background: var(--green-dim);
+    color: var(--green);
+    border-color: rgba(6, 118, 71, 0.25);
+}
+
+.btn-green:hover {
+    background: rgba(6, 118, 71, 0.15);
+    border-color: rgba(6, 118, 71, 0.4);
+    color: var(--green);
+}
+
+/* ─── Toast ─── */
+.toast {
+    position: fixed;
+    bottom: 24px;
+    left: 50%;
+    transform: translateX(-50%);
+    background: var(--text);
+    color: #fff;
+    padding: 8px 20px;
+    border-radius: 4px;
+    font-family: var(--font-mono);
+    font-size: 13px;
+    z-index: 300;
+    animation: fadeSlideIn 0.2s ease, fadeOut 0.3s ease 2s forwards;
+}
+
+@keyframes fadeOut { to { opacity: 0; } }
+
 /* ─── Responsive ─── */
 @media (max-width: 768px) {
     .sidebar { display: none; }