feat(cast): add Tempo wallet session create and revoke commands

[0xKarl98]

Adds the focused create/revoke-local layer needed to mint a temporary session key, bind it to a constrained authorization policy, validate the signed authorization, and persist it for later --tempo.session use.

• Add cast wallet session create

  • generates a temporary secp256k1 session key
  • parses expiry, call scope, and spend limits
  • builds a SessionAuthorizationRequest
  • signs the authorization with the root wallet
  • validates the signed authorization against the session policy
  • stores the active session entry in the local session registry

• Add cast wallet session revoke

  • Just removes a local session entry by session id

[mattsse]

LGTM