JWTVerifier interceptor does not enforce auth

[fbac]

When a request to the server carries the proper JWT, the auth interceptor sets: ctx = context.WithValue(ctx, constants.VerifiedNodeRequestCtxKey{}, true)

Afterwards, no handler actually checks the context value.

This means:

• All endpoints are optionally authenticated - they accept both authenticated and unauthenticated requests.
• The interceptor only validates tokens when they're present, but doesn't enforce their presence.
• The VerifiedNodeRequestCtxKey context value exists but is unused (except in tests).