example(bdk_wallet): add BIP-329 wallet labels example using bip329 crate

[Leeyah-123]

Description

Adds examples/bip329_labels.rs demonstrating how to use bdk_wallet together with the bip329 crate to annotate wallet items with human-readable labels in the BIP-329 JSONL format.

The example covers:

• Creating a wallet from a BIP-39 mnemonic
• Labelling revealed addresses (AddressRecord) with BIP-84 keypath context
• Labelling transactions (TransactionRecord) — enriched with fee and net flow
  from wallet.calculate_fee / wallet.sent_and_received after a sync
• Labelling UTXOs (OutputRecord) with spendable coin-control hints
• Exporting labels to a JSONL file (Labels::export_to_file)
• Reloading and querying efficiently with Labels::into_string_map
• Updating labels in-place (retain + push) and streaming to stdout via
  Labels::export_to_writer

Replaces #383.

Changelog notice

• example(bdk_wallet): add BIP-329 labels example using the bip329 crate

Checklists

All Submissions:

• I've signed all my commits
• I followed the contribution guidelines
• I ran just p before pushing

New Features:

• I've added docs for the new feature

[Leeyah-123]

@ValuedMammal I was assigned this, but the previous PR closed automatically when I renamed the branch.

[ValuedMammal]

Thanks I'll take a look at it and continue researching a potential labels feature in bdk_wallet, though I would note that this looks similar to the existing #222 and we probably don't need both.

[Leeyah-123]

Thanks I'll take a look at it and continue researching a potential labels feature in bdk_wallet, though I would note that this looks similar to the existing #222 and we probably don't need both.

Thanks a lot!
Yes, I'm aware of the existence of that PR, I'm tackling this also as a challenge I was given in BOSS 2026.