feat: GPU rendering + material matching + perf improvements

- GPU: fix Cycles device activation order — set compute_device_type
  BEFORE engine init, re-set AFTER open_mainfile wipes preferences
- GPU: remove _mark_sharp_and_seams edit-mode loop (redundant with
  Blender 5.0 shade_smooth_by_angle), saves ~200s/render on 175 parts
- Material: fix _AFN suffix mismatch — build AF-stripped mat_map keys
  and add prefix fallback in _apply_material_library (blender_render.py)
- Material: production GLB now uses get_material_library_path() which
  checks active AssetLibrary instead of empty legacy system setting
- Admin: RenderTemplateTable multi-select output types (M2M frontend)
- Admin: MaterialLibraryPanel replaced with link to Asset Libraries
- UX: move Toaster to top-left to avoid dispatch button overlap
- SQLAlchemy: add .unique() to all RenderTemplate M2M collection queries
- Logging: flush=True on all Blender progress prints, stdout reconfigure

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

backend/app/tasks/beat_tasks.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 
 import json
 import logging
+from datetime import datetime, timedelta
 
 from celery import shared_task
 
@@ -31,3 +32,51 @@ def broadcast_queue_status() -> None:
         logger.debug("Broadcast queue_update: %s", depths)
     except Exception as exc:
         logger.warning("broadcast_queue_status failed: %s", exc)
+
+
+@shared_task(name="app.tasks.beat_tasks.recover_stuck_cad_files", queue="step_processing")
+def recover_stuck_cad_files() -> None:
+    """Reset CAD files stuck in 'processing' for more than 10 minutes to 'failed'.
+
+    This recovers from worker crashes (container restarts, OOM kills) that leave
+    the processing_status committed as 'processing' with no task running to complete it.
+    Runs every 5 minutes via Celery Beat.
+    """
+    try:
+        from sqlalchemy import create_engine, update, and_
+        from sqlalchemy.orm import Session
+        from app.config import settings
+        from app.models.cad_file import CadFile, ProcessingStatus
+
+        cutoff = datetime.utcnow() - timedelta(minutes=10)
+        sync_url = settings.database_url.replace("+asyncpg", "")
+        engine = create_engine(sync_url)
+        with Session(engine) as session:
+            result = session.execute(
+                update(CadFile)
+                .where(
+                    and_(
+                        CadFile.processing_status == ProcessingStatus.processing,
+                        CadFile.updated_at < cutoff,
+                    )
+                )
+                .values(
+                    processing_status=ProcessingStatus.failed,
+                    error_message="Processing timed out — worker may have crashed. Use 'Regenerate Thumbnail' to retry.",
+                )
+                .returning(CadFile.id, CadFile.original_name)
+            )
+            rows = result.fetchall()
+            session.commit()
+        engine.dispose()
+
+        if rows:
+            names = [r[1] for r in rows]
+            logger.warning(
+                "recover_stuck_cad_files: reset %d stuck file(s) to failed: %s",
+                len(rows), names,
+            )
+        else:
+            logger.debug("recover_stuck_cad_files: no stuck files found")
+    except Exception as exc:
+        logger.error("recover_stuck_cad_files failed: %s", exc)