fix: media thumbnails, product dimensions, inline 3D viewer, GLB export

Bug A: Media Library thumbnails were gray because <img src> cannot send
JWT auth headers. Added useAuthBlob() hook (fetch + createObjectURL) in
MediaBrowser.tsx. Also fixed publish_asset Celery task to populate
product_id + cad_file_id on MediaAsset for thumbnail fallback resolution.

Bug B: Product dimensions now shown in Product Details card with Ruler
icon and "from CAD" label when cad_mesh_attributes.dimensions_mm exists.

Bug C: Replaced 128×128 CAD thumbnail with InlineCadViewer component.
Queries gltf_geometry MediaAssets, fetches GLB via auth fetch → blob URL
→ Three.js Canvas with OrbitControls. Falls back to thumbnail + "Load 3D
Model" button. Polling when GLB generation is in progress.

Bug D: trimesh was in [cad] optional extra but Dockerfile only installed
[dev]. Changed to pip install -e ".[dev,cad]" — trimesh now available in
backend container, GLB + Colors export works.

Also added bbox extraction (STL-first numpy parsing) in render_step_thumbnail
and admin "Re-extract CAD Metadata" bulk endpoint.

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

render-worker/scripts/export_gltf.py

@@ -31,12 +31,50 @@ def parse_args() -> argparse.Namespace:
     parser.add_argument("--output_path", required=True)
     parser.add_argument("--asset_library_blend", default=None)
     parser.add_argument("--material_map", default="{}")
+    parser.add_argument("--sharp_edges_json", default="[]",
+                        help="JSON array of [x, y, z] midpoints (mm) to mark as sharp edges")
     return parser.parse_args(rest)
 
 
+def mark_sharp_edges_by_proximity(midpoints_mm: list, threshold_mm: float = 1.0) -> None:
+    """Mark Blender mesh edges as sharp based on proximity to OCC-derived midpoints.
+
+    midpoints_mm: list of [x, y, z] in mm (from OCC coordinate space).
+    After STL import + scale-apply (mm→m), Blender vertices are in meters, so we
+    convert the edge midpoint back to mm before comparing.
+    threshold_mm: snap distance in mm (default 1.0 mm).
+    """
+    if not midpoints_mm:
+        return
+
+    import bpy  # type: ignore[import]
+
+    for obj in bpy.data.objects:
+        if obj.type != "MESH":
+            continue
+        mesh = obj.data
+        mesh.use_auto_smooth = True
+        mw = obj.matrix_world
+        for edge in mesh.edges:
+            v1 = mw @ mesh.vertices[edge.vertices[0]].co
+            v2 = mw @ mesh.vertices[edge.vertices[1]].co
+            # Convert Blender meters → mm for comparison
+            mid_mm = [
+                (v1.x + v2.x) / 2 * 1000,
+                (v1.y + v2.y) / 2 * 1000,
+                (v1.z + v2.z) / 2 * 1000,
+            ]
+            for hint in midpoints_mm:
+                dist_sq = sum((a - b) ** 2 for a, b in zip(mid_mm, hint))
+                if dist_sq < threshold_mm ** 2:
+                    edge.use_edge_sharp = True
+                    break
+
+
 def main() -> None:
     args = parse_args()
     material_map: dict = json.loads(args.material_map)
+    sharp_edge_midpoints: list = json.loads(args.sharp_edges_json)
 
     import bpy  # type: ignore[import]
 
@@ -52,6 +90,11 @@ def main() -> None:
         bpy.context.view_layer.objects.active = obj
         bpy.ops.object.transform_apply(scale=True)
 
+    # Mark sharp edges for better UV seams
+    if sharp_edge_midpoints:
+        mark_sharp_edges_by_proximity(sharp_edge_midpoints)
+        print(f"Marked sharp edges from {len(sharp_edge_midpoints)} hint points")
+
     # Apply asset library materials if provided
     if args.asset_library_blend and material_map:
         import os