feat: sharp edge pipeline V02, tessellation presets, media cache-bust, GMSH plan

Sharp Edge Pipeline V02:
- export_step_to_gltf.py: replace BRep_Tool.Polygon3D_s (returns None in XCAF) with
  GCPnts_UniformAbscissa curve sampling at 0.3mm step — extracts 17,129 segment pairs
- Inject sharp_edge_pairs + sharp_threshold_deg into GLB extras (scenes[0].extras)
  via binary GLB JSON-chunk patching (no extra dependency)
- export_gltf.py: read schaeffler_sharp_edge_pairs from Blender scene custom props,
  apply via KD-tree to mark edges sharp=True + seam=True (OCC mm Z-up → Blender transform)
- tools/restore_sharp_marks.py: dual-pass (dihedral angle + OCC pairs), updated coordinate
  transform (X, -Z, Y) * 0.001

Tessellation:
- Admin UI: Draft / Standard / Fine preset buttons with active-state highlighting
- Default angular deflection: preview 0.5→0.1 rad, production 0.2→0.05 rad
- export_glb.py: read updated defaults from system_settings

Media / Cache:
- media/service.py: get_download_url appends ?v={file_size_bytes} cache-buster
- media/router.py: Cache-Control: no-cache for all download/thumbnail endpoints

Render pipeline:
- still_render.py / turntable_render.py: shared GPU activation + camera improvements
- render_order_line.py: global render position support
- render_thumbnail.py: updated defaults

Frontend:
- InlineCadViewer: file_size_bytes-aware URL update triggers re-fetch on regeneration
- ThreeDViewer: material panel, part selection, PBR mode improvements
- Admin.tsx: tessellation preset cards, GMSH setting dropdown
- MediaBrowser, ProductDetail, OrderDetail, Orders: various UI improvements
- New: MaterialPanel, GlobalRenderPositionsPanel, StepIndicator components
- New: renderPositions.ts API client

Plans / Docs:
- plan.md: GMSH Frontal-Delaunay tessellation plan (6 tasks)
- LEARNINGS.md: OCC Polygon3D_s None issue + GCPnts fix
- .gitignore: add backend/core (core dump from root process)

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

backend/app/domains/pipeline/tasks/export_glb.py

@@ -69,7 +69,7 @@ def generate_gltf_geometry_task(self, cad_file_id: str):
     eng.dispose()
 
     linear_deflection = float(sys_settings.get("gltf_preview_linear_deflection", "0.1"))
-    angular_deflection = float(sys_settings.get("gltf_preview_angular_deflection", "0.5"))
+    angular_deflection = float(sys_settings.get("gltf_preview_angular_deflection", "0.1"))
 
     step = _Path(step_path_str)
 
@@ -230,7 +230,7 @@ def generate_gltf_production_task(self, cad_file_id: str, product_id: str | None
 
     smooth_angle = float(sys_settings.get("blender_smooth_angle", "30"))
     prod_linear = float(sys_settings.get("gltf_production_linear_deflection", "0.03"))
-    prod_angular = float(sys_settings.get("gltf_production_angular_deflection", "0.2"))
+    prod_angular = float(sys_settings.get("gltf_production_angular_deflection", "0.05"))
 
     scripts_dir = _Path(_os.environ.get("RENDER_SCRIPTS_DIR", "/render-scripts"))
     occ_script = scripts_dir / "export_step_to_gltf.py"
@@ -239,12 +239,14 @@ def generate_gltf_production_task(self, cad_file_id: str, product_id: str | None
 
     prod_geom_glb = step_path.parent / f"{step_path.stem}_production_geom.glb"
     python_bin = _sys.executable
+    sharp_threshold = float(sys_settings.get("sharp_edge_threshold", "20.0"))
     occ_cmd = [
         python_bin, str(occ_script),
         "--step_path", str(step_path),
         "--output_path", str(prod_geom_glb),
         "--linear_deflection", str(prod_linear),
         "--angular_deflection", str(prod_angular),
+        "--sharp_threshold", str(sharp_threshold),
     ]
     log_task_event(
         self.request.id,

backend/app/domains/pipeline/tasks/render_order_line.py

@@ -130,7 +130,7 @@ def render_order_line_task(self, order_line_id: str):
                 logger.info(f"No render template for category_key={category_key!r}, output_type_id={ot_id!r}")
 
             cad_name = cad_file.original_name if cad_file else "?"
-            # Load render_position for rotation values
+            # Load render_position for rotation values (per-product takes priority, falls back to global)
             rotation_x = rotation_y = rotation_z = 0.0
             if line.render_position_id:
                 from app.models.render_position import ProductRenderPosition
@@ -138,6 +138,12 @@ def render_order_line_task(self, order_line_id: str):
                 if rp:
                     rotation_x, rotation_y, rotation_z = rp.rotation_x, rp.rotation_y, rp.rotation_z
                     emit(order_line_id, f"Render position: '{rp.name}' ({rotation_x}°, {rotation_y}°, {rotation_z}°)")
+            elif line.global_render_position_id:
+                from app.models import GlobalRenderPosition
+                grp = session.get(GlobalRenderPosition, line.global_render_position_id)
+                if grp:
+                    rotation_x, rotation_y, rotation_z = grp.rotation_x, grp.rotation_y, grp.rotation_z
+                    emit(order_line_id, f"Global render position: '{grp.name}' ({rotation_x}°, {rotation_y}°, {rotation_z}°)")
 
             emit(order_line_id, f"Starting render for {cad_name} ({len(part_colors)} coloured parts)")
 
@@ -345,6 +351,7 @@ def render_order_line_task(self, order_line_id: str):
             if success:
                 # Create MediaAsset so the render appears in the Media Browser
                 try:
+                    import os as _os
                     from app.domains.media.models import MediaAsset, MediaAssetType as MAT
                     from app.config import settings as _cfg2
                     _ext = str(output_path).rsplit(".", 1)[-1].lower() if "." in str(output_path) else "bin"
@@ -360,6 +367,33 @@ def render_order_line_task(self, order_line_id: str):
                         select(MediaAsset.id).where(MediaAsset.storage_key == _norm_key).limit(1)
                     ).scalar_one_or_none()
                     if not _existing:
+                        # Probe output file for metadata
+                        _file_size = None
+                        _width = None
+                        _height = None
+                        if _os.path.exists(output_path):
+                            try:
+                                _file_size = _os.path.getsize(output_path)
+                            except OSError:
+                                pass
+                            if _ext in ("png", "jpg", "jpeg"):
+                                try:
+                                    from PIL import Image as _PILImage
+                                    with _PILImage.open(output_path) as _im:
+                                        _width, _height = _im.size
+                                except Exception:
+                                    pass
+                        # Snapshot key render settings into render_config
+                        _render_config = None
+                        if isinstance(render_log, dict):
+                            _render_config = {
+                                k: render_log[k]
+                                for k in (
+                                    "renderer", "engine_used", "engine", "samples",
+                                    "device_used", "compute_type", "total_duration_s",
+                                )
+                                if k in render_log
+                            }
                         _asset = MediaAsset(
                             tenant_id=_tenant_id,
                             order_line_id=line.id,
@@ -367,6 +401,10 @@ def render_order_line_task(self, order_line_id: str):
                             asset_type=_at,
                             storage_key=_norm_key,
                             mime_type=_mime,
+                            file_size_bytes=_file_size,
+                            width=_width,
+                            height=_height,
+                            render_config=_render_config,
                         )
                         session.add(_asset)
                         session.commit()

backend/app/domains/pipeline/tasks/render_thumbnail.py

@@ -95,6 +95,38 @@ def render_step_thumbnail(self, cad_file_id: str):
     except Exception:
         logger.exception(f"bbox extraction failed for {cad_file_id} (non-fatal)")
 
+    # Extract sharp edge topology (PCurve-based) if not already present.
+    # This runs on render-worker which has OCP (cadquery's OCC fork).
+    try:
+        from sqlalchemy import create_engine
+        from sqlalchemy.orm import Session
+        from app.config import settings as _cfg3
+        from app.models.cad_file import CadFile as _CadFile3
+        from app.services.step_processor import extract_mesh_edge_data
+
+        _sync_url3 = _cfg3.database_url.replace("+asyncpg", "")
+        _eng3 = create_engine(_sync_url3)
+        with Session(_eng3) as _sess3:
+            _cad3 = _sess3.get(_CadFile3, cad_file_id)
+            _attrs = _cad3.mesh_attributes or {} if _cad3 else {}
+            _step_path3 = _cad3.stored_path if _cad3 else None
+        _eng3.dispose()
+
+        if _step_path3 and "sharp_edge_pairs" not in _attrs:
+            edge_data = extract_mesh_edge_data(_step_path3)
+            if edge_data:
+                _eng3 = create_engine(_sync_url3)
+                with Session(_eng3) as _sess3:
+                    _cad3 = _sess3.get(_CadFile3, cad_file_id)
+                    if _cad3:
+                        _cad3.mesh_attributes = {**(_cad3.mesh_attributes or {}), **edge_data}
+                        _sess3.commit()
+                        n_pairs = len(edge_data.get("sharp_edge_pairs", []))
+                        logger.info(f"Sharp edge data extracted for {cad_file_id}: {n_pairs} sharp edges")
+                _eng3.dispose()
+    except Exception:
+        logger.exception(f"Sharp edge extraction failed for {cad_file_id} (non-fatal)")
+
     # Auto-populate materials now that parsed_objects are available
     try:
         from app.domains.pipeline.tasks.extract_metadata import _auto_populate_materials_for_cad