refactor(templates): remove entity template hierarchy

Remove the entire entity template hierarchy as pages now use PageLayout and compose components directly:
- ProductDetailTemplate.tsx
- EntityDetailTemplate.tsx
- ModelDetailTemplate.tsx
- OrganizationDetailTemplate.tsx
- VendorEntityDetailTemplate.tsx
- All entity section components (EntityBenchmarks, EntityCommunityLinks, etc.)
- Template barrel exports

These templates have been replaced by direct component composition in individual pages.

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

Author: ericyangpan