Complete M11 Creator Studio and M12 Trust & Safety for PC5

- Creator Studio: Visual behavior & property inspector, GLB model importer, binary persistence
- Trust & Safety: 18+ TOS confirmation (DOB removed), creator guidelines & briefing card on join, in-game reporting HUD
- Test Harness: Add --filter, --skip-backend, --skip-godot to run_checkpoint_tests.py

backend/app/routers/assets.py

@@ -6,6 +6,7 @@ from pathlib import Path
 from typing import Optional
 
 from fastapi import APIRouter, Depends, HTTPException, UploadFile, File, Query
+from fastapi.responses import FileResponse
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -241,3 +242,20 @@ async def upload_asset_file(
     await db.commit()
     await db.refresh(asset)
     return asset
+
+
+@router.get("/{asset_id}/file")
+async def get_asset_file(
+    asset_id: int,
+    db: AsyncSession = Depends(get_db),
+):
+    """Download an asset binary file."""
+    asset = await db.get(Asset, asset_id)
+    if asset is None or not asset.file_path or not os.path.exists(asset.file_path):
+        raise HTTPException(status_code=404, detail="Asset file not found")
+    return FileResponse(
+        asset.file_path,
+        media_type=asset.mime_type or "application/octet-stream",
+        filename=os.path.basename(asset.file_path),
+    )
+