feat: per-position camera settings, material alias dialog, product delete, media browser links

- Per-render-position focal_length_mm/sensor_width_mm (DB → pipeline → Blender)
- FOV-based camera distance with min clamp fix for wide-angle lenses
- Unmapped materials blocking dialog on "Dispatch Renders" with batch alias creation
- Material check endpoint (GET /orders/{id}/check-materials)
- Batch alias endpoint (POST /materials/batch-aliases)
- Quick-map "No alias" badges on Materials page
- Full product hard-delete with storage cleanup (MinIO + disk files + orphaned CadFile)
- Delete button on ProductDetail page with confirmation
- Clickable product names in Media Browser (links to product page)
- Single-line render dispatch/retry (POST /orders/{id}/lines/{id}/dispatch-render)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/api/routers/admin.py

@@ -825,3 +825,60 @@ async def import_existing_media_assets(
     await db.commit()
     return {"created": created, "skipped": skipped}
 
+
+@router.delete("/settings/purge-render-media", status_code=status.HTTP_200_OK)
+async def purge_render_media(
+    admin: User = Depends(require_global_admin),
+    db: AsyncSession = Depends(get_db),
+):
+    """Delete all still and turntable MediaAsset records and their backing files.
+
+    This removes rendered images and animations but leaves thumbnails, GLBs,
+    STLs, and USD masters intact.
+    """
+    import logging
+    from pathlib import Path
+    from app.config import settings
+    from app.core.storage import get_storage
+    from app.domains.media.models import MediaAsset, MediaAssetType
+
+    logger = logging.getLogger(__name__)
+    storage = get_storage()
+
+    result = await db.execute(
+        select(MediaAsset).where(
+            MediaAsset.asset_type.in_([MediaAssetType.still, MediaAssetType.turntable])
+        )
+    )
+    assets = result.scalars().all()
+
+    deleted_db = 0
+    deleted_files = 0
+    freed_bytes = 0
+
+    for asset in assets:
+        # Delete backing file
+        key = asset.storage_key
+        try:
+            candidate = Path(key) if Path(key).is_absolute() else Path(settings.upload_dir) / key
+            if candidate.exists():
+                freed_bytes += candidate.stat().st_size
+                candidate.unlink()
+                deleted_files += 1
+            elif hasattr(storage, 'delete'):
+                storage.delete(key)
+                deleted_files += 1
+        except Exception as exc:
+            logger.warning("Could not delete file for asset %s (%s): %s", asset.id, key, exc)
+
+        await db.delete(asset)
+        deleted_db += 1
+
+    await db.commit()
+    return {
+        "deleted_records": deleted_db,
+        "deleted_files": deleted_files,
+        "freed_mb": round(freed_bytes / 1024 / 1024, 1),
+        "message": f"Purged {deleted_db} still/turntable asset(s), freed {round(freed_bytes / 1024 / 1024, 1)} MB",
+    }
+