chore: enable noUncheckedIndexedAccess, better type check

[hyoban]

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• Feature
• Bugfix
• Hotfix
• Other (please describe):

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Changelog

• I have updated the changelog/next.md with my changes.

[linear]

FOL-1503 Enable `noUncheckedIndexedAccess` in `tsconfig.json`

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
follow	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jan 18, 2025 2:36pm

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[follow-reviewer-bot]

Suggested PR Title:

fix: improve type safety with non-null assertions

Change Summary:
Updated typings for better type safety in the application. Adjusted multiple files across main and mobile applications to ensure non-null assertions for potentially undefined values. Added @follow/types as a dev dependency, improved type checks, and minor adjustments to ensure consistent behavior. These changes enhance code reliability and maintainability.

Code Review:
No change requests necessary.