- Add SubpageSectionConfig type to schema.ts - Update config parser to handle sections with album overrides - Refactor SubpageGridView to render TOC + section headers - Add base CSS for subpage-toc and subpage-section in globals.css - Add theme-specific overrides for all 5 themes (minimal, editorial, classic, noir, monograph) - Update gallery.yaml.example and docs/gallery-config.md