Add an encryption key status section to the Settings screen

[Lakes41]

Difficulty: Intermediate
Type: Feature / UI-UX

Background: KeyManager.getKeyInfo() already returns { key, createdAt, needsRotation }, and rotation is currently fully automatic and invisible to the user (triggered silently during initialize()). app/settings.tsx exists and is the natural home for device/security-related visibility, but doesn't currently surface anything about the offline-cache encryption key.

Problem: There's no way for a user (or a support agent troubleshooting a "my offline data disappeared" report) to see when the encryption key was created, whether it's due for rotation, or to manually trigger rotation/cache-clear — all of this state exists in KeyManager but is completely invisible in the UI today.

Expected outcome: A new "Offline Data & Security" section in app/settings.tsx showing the key's creation date (formatted relative, e.g. "Created 12 days ago"), whether rotation is due, and a manual "Rotate encryption key now" action with a clear confirmation dialog explaining the effect on offline data.

Suggested implementation: Add a useKeyInfo() hook (or call keyManager.getKeyInfo() directly in an effect) in settings.tsx; render the info in a Card; wire a button to keyManager.rotateKey() behind a confirmation Alert. This issue pairs naturally with Issue #5/Advanced Issue #3 — the confirmation copy should be accurate about whether rotation currently preserves or clears offline data.

Acceptance criteria:

• Settings screen shows key age and rotation-due status, reading real KeyManager state.
• Manual rotation is gated behind an explicit confirmation with accurate copy about data impact.
• pnpm typecheck passes; screenshot included in the PR per existing NativeWind/UI reviewer conventions.

Likely affected files: app/settings.tsx, src/lib/keyManager.ts, tests/components.test.tsx (or a new settings test).

Labels: feature, ui, security, GrantFox OSS, Maybe Rewarded, Official Campaign | FWC26

[Glam26]

I'd like to contribute this.

My workflow will be to understand the current implementation, make the requested changes incrementally, ensure the solution follows the project's existing architecture and coding style, add regression tests where applicable, and validate everything through the project's standard quality checks before opening a PR.

I'll keep the implementation focused and provide clear documentation of the changes in the PR.

[grantfox-oss]

🦊 GrantFox — @Glam26 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #169)
2. Your PR will be reviewed by the Adamantine-guild maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@Glam26's PR #289 was approved and merged by @Lakes41.

🏆 @Glam26: You earned 40 FoxPoints for this contribution! Your current tier: Builder (1,607 total points). Track your full progress on GrantFox.

👏 Great work, @Glam26! Keep contributing to Adamantine-guild.