Cardano Updates

Enumerates every remaining caller of the deprecated surface after
#5271: production (Cardano.Wallet.hs, Server.hs), old tx builder
(Shelley/Transaction.hs, partially overlaps with #5243), integration
tests (Shared/Transactions.hs, addRequiredSigners in TransactionsNew)
and unit tests (TransactionSpec, TransactionLedgerSpec).

Organises the work into three phases:
  A. reachable without #5243 (4 sites)
  B. unit-test migration (~20 sites, two files)
  C. delete the bridge functions and the three Cardano.Api*
     imports in SealedTx.hs

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).

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.

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.

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.

Replace the cardano-api path
(SealedTx → unsealShelleyTx → TxInMode → toConsensusGenTx → GenTx)
with a direct ledger-native path
(SealedTx → unsafeReadTx :: EraValue Read.Tx → consensusGenTxFromTxRecent → GenTx).

The stored 'EraValue Read.Tx' already knows its era, so the
separate 'readCurrentEra' query is no longer needed, and
'TxInMode' / 'toConsensusGenTx' / 'unsealShelleyTx' /
'UnsealException' all become unused.

Deletes:
  - Cardano.Wallet.Primitive.Ledger.Shelley.unsealShelleyTx
  - Cardano.Wallet.Primitive.Ledger.Shelley.UnsealException
  - cardano-api 'TxInMode' import in primitive
  - cardano-api 'toConsensusGenTx' import in network-layer

Adds 'unsafeReadTx' to the re-export of 'SealedTx' in
Cardano.Wallet.Primitive.Types.Tx. Step 1 of SealedTx decommission
plan. One fewer caller of 'cardanoTxIdeallyNoLaterThan'; the
submission path no longer touches cardano-api.

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 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.

Following the migration of parsePartialTx to deserializeTx,
cardanoTxInExactEra has no external callers. Remove it along
with the now-redundant Data.Data import in SealedTx.hs.

Replace cardanoTxInExactEra (cardano-api path) with
deserializeTx (ledger-native) in the redeemer-bearing
partial tx parser. Pattern-matches on RecentEra era so
the era singleton witnesses the target ledger type.

One fewer caller of cardano-api's
'deserialiseFromCBOR / InAnyCardanoEra Cardano.Tx' path.
'fromCardanoApiTx' → direct use of 'Read.Tx era' unwrapped
into 'Write.Tx era'.

Introduce sealedTxFromLedgerTx :: Read.IsEra era => Read.Tx era -> SealedTx.
Serialises via Read.serializeTx (ledger-native) and wraps in EraValue
without any cardano-api involvement.

Migrate sealWriteTx in Transaction.Ledger.hs to use the new
constructor, pattern-matching on RecentEra to witness the era.
Removes the toCardanoApiTx -> sealedTxFromCardano' roundtrip,
dropping the Cardano.Api.Extra import from that module.

Step 2a 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 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.

Enumerates every remaining caller of the deprecated surface after
#5271: production (Cardano.Wallet.hs, Server.hs), old tx builder
(Shelley/Transaction.hs, partially overlaps with #5243), integration
tests (Shared/Transactions.hs, addRequiredSigners in TransactionsNew)
and unit tests (TransactionSpec, TransactionLedgerSpec).

Organises the work into three phases:
  A. reachable without #5243 (4 sites)
  B. unit-test migration (~20 sites, two files)
  C. delete the bridge functions and the three Cardano.Api*
     imports in SealedTx.hs

Introduce sealedTxFromLedgerTx :: Read.IsEra era => Read.Tx era -> SealedTx.
Serialises via Read.serializeTx (ledger-native) and wraps in EraValue
without any cardano-api involvement.

Migrate sealWriteTx in Transaction.Ledger.hs to use the new
constructor, pattern-matching on RecentEra to witness the era.
Removes the toCardanoApiTx -> sealedTxFromCardano' roundtrip,
dropping the Cardano.Api.Extra import from that module.

Step 2a of SealedTx decommission plan.

Following the migration of parsePartialTx to deserializeTx,
cardanoTxInExactEra has no external callers. Remove it along
with the now-redundant Data.Data import in SealedTx.hs.

Replace cardanoTxInExactEra (cardano-api path) with
deserializeTx (ledger-native) in the redeemer-bearing
partial tx parser. Pattern-matches on RecentEra era so
the era singleton witnesses the target ledger type.

One fewer caller of cardano-api's
'deserialiseFromCBOR / InAnyCardanoEra Cardano.Tx' path.
'fromCardanoApiTx' → direct use of 'Read.Tx era' unwrapped
into 'Write.Tx era'.

Replace the cardano-api path
(SealedTx → unsealShelleyTx → TxInMode → toConsensusGenTx → GenTx)
with a direct ledger-native path
(SealedTx → unsafeReadTx :: EraValue Read.Tx → consensusGenTxFromTxRecent → GenTx).

The stored 'EraValue Read.Tx' already knows its era, so the
separate 'readCurrentEra' query is no longer needed, and
'TxInMode' / 'toConsensusGenTx' / 'unsealShelleyTx' /
'UnsealException' all become unused.

Deletes:
  - Cardano.Wallet.Primitive.Ledger.Shelley.unsealShelleyTx
  - Cardano.Wallet.Primitive.Ledger.Shelley.UnsealException
  - cardano-api 'TxInMode' import in primitive
  - cardano-api 'toConsensusGenTx' import in network-layer

Adds 'unsafeReadTx' to the re-export of 'SealedTx' in
Cardano.Wallet.Primitive.Types.Tx. Step 1 of SealedTx decommission
plan. One fewer caller of 'cardanoTxIdeallyNoLaterThan'; the
submission path no longer touches cardano-api.