feat: add Firebase App Check for device attestation

[felippemsc]

Summary

Add Firebase App Check integration for device attestation during registration. The SDK now supports sending attestation tokens, while remaining provider-agnostic.

Changes

Phase 1A - Apple Setup:

• Update Bundle ID to io.signedshot.capture
• Add App Attest capability and entitlements

Phase 1B - Firebase Setup:

• Add Firebase SDK dependency (FirebaseAppCheck)
• Initialize Firebase and App Check on app launch
• Configure AppAttestProvider (devices) / AppCheckDebugProvider (simulator)
• Add GoogleService-Info.plist to .gitignore

Phase 1D - Attestation Token Support:

• SDK: Add attestationToken parameter to registerDevice()
• SDK: Send X-Attestation-Token header when token provided
• App: Get Firebase App Check token before registration
• App: Add reset device functionality (long press shield icon)
• App: Replace print statements with os.log Logger

Notes

• Currently using Debug Provider due to App Attest 403 issue (to be resolved before App Store release)
• End-to-end flow tested and working with Debug Provider

Test plan

• Build succeeds on simulator and device
• Device registration works with Debug Provider token
• Backend verifies token and returns method: app_check in JWT
• Sidecar validation shows correct attestation info