Fix stale DB connections, add Why Bourbonacci section, harden auth

- Add pool_pre_ping and pool_recycle to prevent lost connection errors on idle pool
- Add Why Bourbonacci card to about page
- Redirect to login on 401 in API layer
- Check JWT expiry in isLoggedIn instead of just token presence

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

backend/app/database.py

@@ -4,7 +4,7 @@ from sqlalchemy.orm import DeclarativeBase
 from app.config import settings
 
 
-engine = create_async_engine(settings.database_url, echo=False)
+engine = create_async_engine(settings.database_url, echo=False, pool_pre_ping=True, pool_recycle=1800)
 AsyncSessionLocal = async_sessionmaker(engine, expire_on_commit=False)