Feat: Implement "Two Pathways" Homepage UI

Redesign src/pages/index.astro to implement the "I know what I want" vs "Help me choose" navigation. Create a clear hero section with the prompt "What are you here to learn today?" and two distinct call-to-action buttons. "I know what I want" should link to the filterable library, and "Help me choose" should navigate or scroll to the existing category folders.