Cardano Updates

## Scope

PR for #5285 under parent #5237 / tracker #5243. This PR migrates
`mkUnsignedTransaction` / `mkUnsignedTx` to ledger-native unsigned body
construction, switches the remaining certificate call sites to
ledger-native certificates, and deletes the obsolete
`Cardano.Wallet.Transaction.Delegation` and
`Cardano.Wallet.Transaction.Voting` helper modules after the migrated
path is proved.

The PR was reopened after Copilot review feedback to remove builder
duplication, clean up the coin conversion alias, and add burn-direction
parity coverage. Those follow-up tasks are tracked as T014-T016 in
`tasks.md` and implemented in
`2826a82dab62abe2c515b4d8179e93b3aecdbae5`.

## Artifacts

- Spec:
https://github.com/cardano-foundation/cardano-wallet/blob/5285-unsigned-ledger/specs/009-unsigned-ledger-builder/spec.md
- Plan:
https://github.com/cardano-foundation/cardano-wallet/blob/5285-unsigned-ledger/specs/009-unsigned-ledger-builder/plan.md
- Tasks:
https://github.com/cardano-foundation/cardano-wallet/blob/5285-unsigned-ledger/specs/009-unsigned-ledger-builder/tasks.md
- Worker brief:
https://github.com/cardano-foundation/cardano-wallet/blob/5285-unsigned-ledger/specs/009-unsigned-ledger-builder/briefs/T010-T013.md

## Integration-test policy

No files under `lib/integration/**` may be modified in this PR. Existing
integration tests may run unchanged only as verification signal.

## Verification

- Baseline: `./gate.sh` passed on branch bootstrap at `59b3bcd110`:
format check, fast-dev cabal build for
`cardano-wallet:lib:cardano-wallet` + `cardano-wallet-unit:unit`,
focused Shelley transaction specs (`44 examples, 0 failures`), and
`hlint` (`No hints`).
- Implementation: `./gate.sh` passed at
`16e308998640e780aae209e2f55c4e88072bc9df`: fourmolu, cabal-fmt, nixfmt,
library + unit build, focused Shelley transaction specs (`44 examples, 0
failures`), and `hlint` (`No hints`).
- CI warning repair: `nix build --quiet .#unit-cardano-wallet-unit`
passed at `3eacd6b5c4deaa874d12a6758bfab7a3f7b929ff` after removing
redundant test imports that failed full-unit CI with
`-Werror=unused-imports`.
- Pre-review finalization: final-head CI was green at
`82ab728b9617ee1d961505cacc2d8a768794a57a` before the PR was reopened
for Copilot review refinements.
- Copilot review response: focused `ledger script-witness parity` passed
at `2826a82dab62abe2c515b4d8179e93b3aecdbae5` with `8 examples, 0
failures`; `./gate.sh` passed with `45 examples, 0 failures`; HLint
reported `No hints`.
- Finalization: `./gate.sh` passed again before the final drop-gate
commit, with Shelley transaction specs `45 examples, 0 failures` and
HLint `No hints`.
- Removal guard: `rg -n "Cardano.Wallet.Transaction.(Delegation|Voting)"
lib/wallet lib/unit` prints nothing.
- Integration guard: `git diff --name-only origin/master...HEAD | rg
'^lib/integration/'` prints nothing.
- Unsigned-builder guard: `rg -n "createTransactionBody|TxBodyContent"
lib/wallet/src/Cardano/Wallet/Shelley/Transaction.hs` prints one
remaining `Cardano.getTxBodyContent` reference in `signTransaction`
(`Transaction.hs:375`), which is outside the migrated unsigned builder
path and remains scoped to #5289.
- Final branch audit at `2d33771ca258b9945902fcb7a776a522b4f038ba`:
every branch commit passes the message gate;
`specs/009-unsigned-ledger-builder/tasks.md` has no open tasks;
`gate.sh` is absent at final HEAD.

## Current phase

Ready for review at `2d33771ca258b9945902fcb7a776a522b4f038ba`.
Final-head CI was triggered by the push and is pending.

Closes #5285.