Apply scope policy to OpenID4VP / auth-code flow token issuance

Context

#4179 added server-side scope policy enforcement (profile-only / passthrough / dynamic) to the S2S vp_token flow in handleS2SAccessTokenRequest. The OpenID4VP / authorization-code flow takes a separate path to createAccessToken that does not invoke grantedScopesForPolicy — so scope policy is currently not enforced for that flow.

Problem

In auth/api/iam/openid4vp.go the auth-code handler uses oauthSession.Scope (the raw requested scope) and passes it directly to createAccessToken. This means:

• profile-only: extra scopes are NOT rejected
• dynamic: the AuthZen PDP is NOT called; extra scopes pass through without evaluation
• passthrough: works by accident (raw scope is forwarded)

A client going through the auth-code flow can request arbitrary extra scopes and receive them in the issued access token — bypassing the policy that's enforced on the S2S path.

Expected behaviour

Same as the S2S flow:

• Look up the credential profile via FindCredentialProfile
• Reject profile-only + extras
• Call the AuthZen PDP for dynamic
• Issue token with only granted scopes

Related

• Parent PRD: #4144
• Introduced gap: #4179

Start in auth/api/iam/openid4vp.go and trace the authorization-code path through createAccessToken. Compare it with handleS2SAccessTokenRequest and grantedScopesForPolicy, including FindCredentialProfile and the profile-only, dynamic, and passthrough cases. Done means extra scopes are rejected or evaluated as appropriate and issued tokens contain only granted scopes.