Missing audience validation in Pocket ID client credentials grant

Pocket ID is an OIDC provider that allows users to authenticate with their passkeys to services. From 1.11.0 until 2.10.0, createTokenFromClientCredentials in backend/internal/service/oidc_service.go accepts the client-controlled resource parameter and embeds it directly in the access token aud claim without validating that the audience is registered or that the requesting client may access it. Any authenticated OIDC client can therefore obtain a Pocket ID-signed token naming another client or an arbitrary audience. The /api/oidc/introspect endpoint cannot distinguish the unauthorized token because it treats a token as active when the introspecting client's identifier matches the attacker-selected audience. In deployments where resource servers trust Pocket ID access tokens for service-to-service authorization, this bypasses audience-based access controls and can permit unauthorized data access or actions; deployments that do not use these tokens for resource-server authorization have no immediate exploitable impact. This issue is fixed in version 2.10.0.