feat(identity-wallet): add PdsAuthScreen component
- Create PdsAuthScreen component that follows AuthenticatingScreen pattern
- Accepts pdsUrl, onnext, onback props
- Shows initial state with PDS connection prompt and button
- On button press, sets authenticating=true and calls startPdsAuth(pdsUrl)
- Shows spinner while authenticating
- Maps ClaimError codes to user-friendly messages:
- UNAUTHORIZED: 'Authentication was denied. Please try again.'
- NETWORK_ERROR: 'Network error. Check your connection and try again.'
- Other: 'Authentication failed. Please try again.'
- On error, shows error message with 'Try Again' and 'Back' buttons
- On success, calls onnext() to navigate to next step
- Styling follows existing screen patterns with centered layout
- Type checked successfully with pnpm check