# Plan: Migrate blender_render.py from STL to GLB Import

## Kontext

`render_blender.py` (backend service) correctly converts STEP→GLB via OCC and passes the GLB path as `argv[0]` to `blender_render.py`. However, `blender_render.py` still calls `_import_stl()` which uses `bpy.ops.wm.stl_import()` and `_scale_mm_to_m()`. The GLB from OCC is already in metres (scaled 0.001 internally by `export_step_to_gltf.py`), so no scaling is needed.

`still_render.py` already has a correct `_import_glb()` implementation using `bpy.ops.import_scene.gltf()` — this serves as the reference.

This caused render failures for order SA-2026-00099: Blender tried to STL-import a `.glb` file → silent failure → cancelled renders.

## Betroffene Dateien

| Datei | Änderung |
|-------|----------|
| `blender-renderer/blender_render.py` | Replace `_import_stl` with `_import_glb`, remove `_scale_mm_to_m`, rename `stl_path` → `glb_path` |

## Tasks (in Reihenfolge)

### [x] Task 1: Replace `_import_stl()` with `_import_glb()` in `blender_render.py`

- **Datei**: `blender-renderer/blender_render.py`
- **Was**:
  1. Replace `_import_stl()` function (lines ~206-289) with `_import_glb()` modeled on `still_render.py:196-229`:
     - Use `bpy.ops.import_scene.gltf(filepath=glb_path)`
     - Collect imported mesh objects
     - No scaling needed (GLB already in metres)
  2. Remove `_scale_mm_to_m()` function (lines ~166-182) — no longer needed
  3. Remove all calls to `_scale_mm_to_m(parts)` (Mode A ~line 466, Mode B ~line 386)
  4. Replace all calls to `_import_stl(stl_path)` with `_import_glb(glb_path)` (Mode A ~line 464, Mode B ~line 384)
  5. Rename variable `stl_path` → `glb_path` throughout (line 65, 715, and all references)
  6. Update docstring/comments referencing STL
- **Akzeptanzkriterium**: `blender_render.py` imports GLB via `bpy.ops.import_scene.gltf()`, no STL references remain, no mm→m scaling
- **Abhängigkeiten**: keine

## Migrations-Check

Keine Migration nötig — reine Script-Änderung.

## Reihenfolge-Empfehlung

1. Task 1 (blender_render.py)
2. Rebuild render-worker: `docker compose up -d --build render-worker`
3. Test: trigger a thumbnail render or order render and check logs

## Risiken / Offene Fragen

1. **`_apply_material_library()`** and **`_resolve_part_name()`** work on Blender objects after import — they should work identically regardless of import format (STL vs GLB).
2. **Auto-camera computation** uses bounding box of imported objects — works the same with GLB meshes.
3. **`turntable_render.py`** and **`turntable_setup.py`** — need to check if they also still use STL import. If so, they need the same fix (but out of scope for this plan unless confirmed).