fix: add NSBluetoothAlwaysUsageDescription purpose string

[ovitrif]

Summary

Stacked on #515

• Add NSBluetoothAlwaysUsageDescription to Info.plist build settings to resolve App Store Connect warning 90683
• CoreBluetooth is linked as a transitive dependency of BitkitCore (Rust library) but is not actively used by the app

Test plan

• Open project in Xcode, verify the key appears in Build Settings > Info.plist Values
• Build and check the generated Info.plist in build products contains the key
• Upload new build to App Store Connect and confirm warning 90683 is gone - @piotr-iohk

🤖 Generated with Claude Code

[ovitrif]

Self-checks:

• build in Xcode and run on iPhone

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• Open project in Xcode, verify the key appears in Build Settings > Info.plist Values

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• Build and check the generated Info.plist in build products contains the key

[claude]

Code review

Issue: Missing CHANGELOG.md entry

This is a fix: PR, which per CLAUDE.md requires exactly one changelog entry:

ALWAYS add exactly ONE entry per PR under ## [Unreleased] in CHANGELOG.md for feat: and fix: PRs

The ## [Unreleased] section is currently empty. Please add an entry like:

### Fixed
- Add NSBluetoothAlwaysUsageDescription to resolve App Store Connect warning ITMS-90683 #518

[piotr-iohk]

Upload new build to App Store Connect and confirm warning 90683 is gone - @piotr-iohk

Since we need to update build no to upload, I'll do in base PR.