Nested Routes with View Stack

Demonstrates manage_views=True with nested route hierarchy. Each route component returns a View with its own AppBar.

• Swipe-back and AppBar back button work automatically
• Home is a pathless root, so it's always in the view stack
• / → 1 view (Home)
• /products → 2 views (Home, Products) — back to Home
• /products/1 → 3 views (Home, Products, Product Details) — back to Products