6 — Move HomePage styles to scoped CSS

Problem: custom.css is 1318 lines with 79 !important declarations. ~600 lines are HomePage-specific (.hero, .blob, .pipeline, .model-card, etc.) that fight VitePress's .vp-doc specificity. All other components use <style scoped>.

Action:

• Move homepage-specific CSS from custom.css into <style scoped> in HomePage.vue
• Keep only brand variables, VitePress overrides, and about-page styles in custom.css
• Use :deep() where needed for nested VitePress elements

Files touched:

• .vitepress/theme/custom.css
• .vitepress/theme/components/HomePage.vue

Done when: custom.css reduced to ~400 lines (brand vars + global overrides only). Zero homepage-specific classes in global CSS.