feat: add change utxo dropped when full swap use case

[Battambang]

Note

Improves PSBT filling to handle bridge/full-balance swap templates reliably.

• In AccountUseCases.#fillPsbt, detect when the built PSBT has fewer outputs than the template and re-build using fixed recipients for all template outputs to preserve change and maintain untouchedOrdering.
• Adds unit tests covering preserving bridge deposit + OP_RETURN + change, and a fallback rebuild path when change is dropped; updates mocks to include unsigned_tx.output.
• Updates snap.manifest.json source shasum.

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