chore: Rename project from WebTriviasMulti to Trivy

- Update all code references to new name
- Rename design document
- Update package.json
- Update frontend titles and branding

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/scripts/seed_achievements.py

@@ -1,6 +1,6 @@
 import asyncio
 import sys
-sys.path.insert(0, '/root/WebTriviasMulti/backend')
+sys.path.insert(0, '/root/Trivy/backend')
 
 from sqlalchemy import select
 from app.models.base import get_async_session