Cardano Updates

Server.hs carried a local copy of sealWriteTx that re-entered
cardano-api (toCardanoApiTx + sealedTxFromCardano) to wrap an already
ledger-native balanceTx result. Import the ledger-native sealWriteTx
from Transaction.Ledger instead; the local helper goes away. Two call
sites now pass Write.recentEra explicitly.

Drops the cardano-api bridges cardanoEraFromRecentEra, toCardanoApiTx
and W.sealedTxFromCardano from this module's imports.

The signedTx wrapping in Cardano.Wallet went through
toCardanoApiTx -> inAnyCardanoEra -> sealedTxFromCardano purely to
smuggle the already-ledger tx back through cardano-api. Use the
existing ledger-native sealWriteTx from Transaction.Ledger instead
(now exported). Drops the two cardano-api bridges inAnyCardanoEra and
sealedTxFromCardano from this module.

Also refresh the sealWriteTx haddock (the function has been ledger-
native since the last revamp; the stale comment claimed otherwise).

The function has been an ADP-3077 TODO stub (error "...") for a long
time; the commented-out cardano-api body still referenced
getSealedTxBody and sealedTxFromCardanoBody, which blocks their
removal. Drop the dead block and note that a future implementation
should operate on Read.Tx era via reqSignerHashesTxBodyL.

Mirror the TransactionsNew.hs:getMetadataFromTx port: project metadata
directly from Read.Tx era via Meta.getMetadata . Meta.getEraMetadata
instead of round-tripping through cardano-api. Drops the two callers
of cardanoTxIdeallyNoLaterThan in this file and the Cardano.Api /
ApiEra qualified imports.

Replace cardano-api round-trip with direct Read.Tx era projection via
Meta.getMetadata . Meta.getEraMetadata. Drops the four callers of
cardanoTxIdeallyNoLaterThan in this file (the cardano-api re-decode
was only used to feed getTxBody/txMetadata).

No behavioural change: the ledger metadata path is what Server.hs and
DB.TransactionInfo already use.

Introduce sealedTxWitnessCount :: SealedTx -> Int, counting VKey
plus bootstrap witnesses via 'addrTxWitsL'/'bootAddrTxWitsL' on the
stored 'EraValue Read.Tx'. Byron txs counted as 0 (wallet doesn't
construct them through SealedTx).

Migrate Server.hs's two 'length $ getSealedTxWitnesses sealedTx'
sites (redeemer and witness accounting) to use it. Drops
'getSealedTxWitnesses' from Server.hs's import list.

Step 2b of SealedTx decommission plan.

Replace compareOnCBOR's roundtrip through cardano-api
(cardanoTx → Cardano.serialiseToCBOR) with the raw bytes
already stored in SealedTx.serialisedTx. Identical
comparison outcome, one fewer caller of
cardanoTxIdeallyNoLaterThan. Step 1 of SealedTx
decommission plan.

Five-step plan to remove the three remaining Cardano.Api imports from
lib/primitive/lib/Cardano/Wallet/Primitive/Types/Tx/SealedTx.hs by
eliminating the bridge functions (cardanoTxIdeallyNoLaterThan,
cardanoTxInExactEra, sealedTxFromCardano*, getSealedTxBody,
getSealedTxWitnesses, cardanoApiTxToReadTx).

Replace mkUnsignedTx + mkByronWitness/mkShelleyWitness with
mkLedgerTx + mkByronWitnessLedger/mkShelleyWitnessLedger in
the duplicated test module.

All 8 golden hex string tests pass — ledger-native construction
produces byte-identical CBOR to the cardano-api construction.

Replace mkUnsignedTx + mkByronWitness/mkShelleyWitness with
mkLedgerTx + mkByronWitnessLedger/mkShelleyWitnessLedger in
the duplicated test module.

All 8 golden hex string tests pass — ledger-native construction
produces byte-identical CBOR to the cardano-api construction.