refactor: update QR scanner to use current Expo Camera API

[Phantomcall]

Update QR scanner to use current Expo Camera API

Summary

Replace the legacy expo-camera/legacy import with the supported CameraView component from the current Expo Camera API. Removes the ESLint suppression workaround for unresolved imports.

Changes

• app/access-scanner.tsx:
  • Replace Camera from expo-camera/legacy with CameraView from expo-camera
  • Replace CameraType.back enum with facing="back" string prop
  • Replace onBarCodeScanned with onBarcodeScanned
  • Replace barCodeScannerSettings with barcodeScannerSettings (camelCase key: barcodeTypes)
  • Replace BarCodeScanningResult type with BarcodeScanningResult
  • Remove // eslint-disable-next-line import/no-unresolved suppression comment

Verification

• QR scanning still accepts valid GuildPass access payloads and navigates to /access-check
• Invalid QR payloads still show error card with "Scan Again" button
• Camera permission denied / permanently denied states remain functional
• ESLint no longer suppressed for the camera import

Type of change

• Refactor (no functional changes)

Acceptance Criteria

• expo-camera/legacy is no longer imported
• ESLint suppression for camera import is removed
• QR scanning still accepts valid GuildPass access payloads
• Invalid QR payloads still show a clear error and allow scanning again
• Camera permission denied and permanently denied states remain usable

closes #48

[Lakes41]

The workflow is still being rebuilt so this was do @Phantomcall