QR scan entry point for OID4VP Authorization Requests

### Description
Extend the existing `/scan` page to also detect and route OID4VP Authorization Request QR codes. A presentation request URI typically looks like:

### Acceptance criteria
- [ ] The scanner distinguishes between an issuance offer URI and a presentation request URI
- [ ] On detecting an OID4VP request, the user is routed to `/presentation/request`
- [ ] Unrecognised or malformed URIs show a clear error state
- [ ] The parsed request object (or `request_uri`) is stored in a state provider, accessible downstream
- [ ] Unit tests cover the URI-type detection logic