Release 3.2.0

## Milestone

3.2.0

## Commit

TBD

## Summary

`bdk_wallet` `v3.2.0` introduces unstable PSBT construction and fee-bumping APIs built on [`bdk-tx`](https://github.com/bitcoindevkit/bdk-tx), requiring the `bdk-tx` feature and `--cfg bdk_wallet_unstable`; these APIs may change in minor releases. Wallet-owned signing and policy APIs are deprecated in favor of caller-owned keys and explicit spending conditions. The new `Wallet::try_finalize_psbt` provides per-input finalization results. This release also includes several bug fixes and improvements.

## What's changed

- release/3.x: Deprecate wallet-owned signing APIs (backport of [#505](https://github.com/bitcoindevkit/bdk_wallet/pull/505)) [#536](https://github.com/bitcoindevkit/bdk_wallet/pull/536)
- Fix ChangeSet write-once invariants [#517](https://github.com/bitcoindevkit/bdk_wallet/pull/517)
- chore: Update rust edition to 2024 in Cargo.toml [#425](https://github.com/bitcoindevkit/bdk_wallet/pull/425)
- build(deps): bump actions/stale from 10.3.0 to 10.4.0 [#515](https://github.com/bitcoindevkit/bdk_wallet/pull/515)
- build(deps): bump actions/checkout from 6 to 7 [#504](https://github.com/bitcoindevkit/bdk_wallet/pull/504)
- build(deps): bump codecov/codecov-action from 6.0.0 to 7.0.0 [#498](https://github.com/bitcoindevkit/bdk_wallet/pull/498)
- fix(wallet): add support for bip-431 rule 2 [#478](https://github.com/bitcoindevkit/bdk_wallet/pull/478)
- feat: Add Wallet::create_psbt [#516](https://github.com/bitcoindevkit/bdk_wallet/pull/516)
- feat: expose detailed try_finalize_psbt outcomes [#433](https://github.com/bitcoindevkit/bdk_wallet/pull/433)
- chore(ci): add stale issue triage workflow [#497](https://github.com/bitcoindevkit/bdk_wallet/pull/497)
- docs(wallet,params): Fix doc for LoadParams::two_path_descriptor [#510](https://github.com/bitcoindevkit/bdk_wallet/pull/510)

## Steps

- [x] Create new release issue; label and triage
- [x] Archive done PRs on the project board
- [x] Write the Summary and Release Notes
- [x] Create PR bumping the crate version and update CHANGELOG.md
- [ ] Wait for CI, review, and merge
- [ ] Tag the merge commit (--sign --edit)
- [ ] git push --tags
- [ ] cargo publish (--dry-run)
- [ ] Publish GitHub release page
- [ ] Announce on socials (discord, X, nostr, etc.)