feat: implement cached form prefilling for reusable fields

[Michvista]

Closes #401

Summary

• add AsyncStorage-backed caching for reusable form values with 90-day TTL pruning
• prefill empty fields across forms and show non-intrusive cached-value suggestions
• let users clear cached form data from mobile settings
• document the caching strategy and add tests for service + multi-form behavior

What changed

• introduced formCache service and useFormCache hook
• integrated cached suggestions into MobileFormInput
• wired profile edit and registration flows to read/write shared cached values
• added “Clear Cached Form Data” under Settings > Privacy
• documented cache keys, lifecycle, and manual test flow

Testing

• npm test -- --runInBand tests/services/formCache.test.ts
• npm test -- --runInBand tests/hooks/useFormCache.test.ts

Notes

• direct push to upstream origin was not permitted from this machine, so this branch was pushed to the fork remote and is ready for PR creation from there
• full repo TypeScript check still has unrelated existing errors outside the scope of this issue

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[RUKAYAT-CODER]

kindly resolve conflict and fix workfow.

[Michvista]

Fixed the conflicts ma'am