docs: add JSDoc for timezone helpers

[vikas-mallikarjuna]

🏛️ PACT Pull Request

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1. Related Issue

Closes #68

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2. Summary of Changes

Added complete JSDoc documentation for the timezone helper functions
localToUtc and utcToDatetimeLocalInput in src/lib/time.ts.

The documentation includes parameters, return values, supported date/time
formats, timezone information, and usage examples.

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3. Motivation & Context (Optional for Micro-PRs)

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4. Implementation Details (Optional for Micro-PRs)

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5. Testing & Local Validation

• [ x ] npm run lint — ESLint passed with 0 errors
• [ x ] npx tsc --noEmit — TypeScript strict check passed with 0 errors
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If this is a documentation-only or micro PR, specify which verification was performed:

npm run lint, npx tsc --noEmit, and git diff --check completed successfully.

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6. UI & Visual Changes (Optional)

• No UI changes (This PR does not alter visual styling, layout, or components)
• UI modifications included:
  • Tested responsive scaling on mobile (375px), tablet (768px), and desktop (1280px+)
  • Adhered to the luxury Obsidian & Gold palette (docs/DESIGN_SYSTEM.md)
  • Verified visible focus states and contrast ratios (WCAG AA)

Before	After
(attach before screenshot/recording)	(attach after screenshot/recording)

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7. Database & Security Impact (Optional)

• No database or security-sensitive changes
• Database modifications included:
  • Sequential migration added in supabase/migrations/
  • Row Level Security (RLS) policies verified with auth.uid()
  • No destructive schema changes on active columns
• Security modifications included:
  • Server Action input validated with Zod
  • User identity verified with supabase.auth.getUser()

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8. Documentation Impact (Optional)

• Documentation updated to reflect changes (e.g., in docs/ or README.md)
• Documentation updates not required for this change

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9. Contributor Quality Checklist

Please verify the following before requesting a maintainer review:

• [ x ] 🌱 Micro-Contribution Fast-Path: This is a targeted Good First Issue / 5–30 minute micro-change (single file, verified locally).
• [ x ] My PR has a single, focused scope (avoiding unrelated formatting or refactoring).
• [ x ] I have read and followed PACT's Contributing Guide.
• [ x ] I confirm that zero secrets, API keys, private tokens, or .env.local files are included in this PR.
• My branch was created from the latest upstream/main with an appropriate prefix (e.g., feat/, fix/, docs/, ui/).
• [ x ] My commits follow the Conventional Commits format (type(scope): description).
• [ x ] I have linked the target issue in Section 1 above.
• [ x ] I have reviewed my own git diff to ensure no stray files or debugging artifacts were committed.

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10. Reviewer Notes (Optional)

[github-actions]

👋 Welcome to PACT OS, @vikas-mallikarjuna! 🚀

Thank you for taking the time to open your first pull request on PACT! We are thrilled to have you here in our open-source community.

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[vikas-mallikarjuna]

Thank you! I'm glad I could contribute to PACT OS. 🚀