Add One Tiny Clean to productivity tools

[zigzag-dev26]

Summary

• adds the already-approved One Tiny Clean submission to productivity-tools
• uses the existing ai-productivity category so the entry satisfies ProductivityCategory
• links the free, no-account web tool as the primary URL
• includes balanced pros, limitations, and non-medical positioning

Closes #44.

Verification

• npm run lint (passes; existing warnings only)
• npm run build
• local generated detail page returns HTTP 200 at /productivity-tools/tools/one-tiny-clean
• generated page is indexable, self-canonical, and links to https://nudgeclean.app/tiny-clean without affiliate attributes

[vercel]

@zigzag-dev26 is attempting to deploy a commit to the jrsaint's projects Team on Vercel.

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