Migrate Compatible.Certificate callers to Exp.Certificate
Replace the remaining five imports of Cardano.Api.Compatible.Certificate with direct ledger-level construction of Exp.Certificate. This removes the indirection through the Compatible API so the old Certificate type in cardano-api can be deprecated. The era-varying helpers (StakeRegistrationRequirements, Delegatee type families) are inlined at each callsite. MIR and GenesisKeyDelegation certificates remain pinned to BabbageEra since their on-chain serialization is uniform across Shelley→Babbage.