test: add unit tests for template/extension page components

[ulises-jeremias]

Describe the feature

Add unit tests for catalog page helpers/components (parsing templates.json, filtering).

Use Case

Regressions in catalog rendering are easy after AI/ML catalog growth.

Proposed Solution

Extend existing vitest/jest setup; prefer pure functions over brittle snapshots.

Other Information

Maintainer-seeded Hacktoberfest issue.

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

Version used

website @ main

Environment details (OS name and version, etc.)

n/a (docs/site contribution)