fix: TransactionBaseModel.computeSignatureKey() must propagate exceptions

[ericleponner]

Description:

Changes below update TransactionBaseModel.computeSignatureKey() method.
Current method code swallows exceptions which prevents to use them for user error reporting.
Changes below make sure that:

• TransactionBaseModel.computeSignatureKey() propagates errors
• callers correctly handle bubbling errors

For archive purpose, here is the calling tree of TransactionBaseModel.computeSignatureKey():

TransactionBaseModel.computeSignatureKey()                  renderer/utils/transactionSignatureModels/transaction.model.ts
    computeSignatureKey()                                      renderer/utils/transactionSignatureModels/index.ts

        usersPublicRequiredToSign() OK                              renderer/utils/transactionSignatureModels/index.ts
            isSignableTransaction() OK                                  renderer/utils/transactionSignatureModels/index.ts
            collectRequiredKeys() OK                                    renderer/utils/index.ts
            signTransactions() OK                                       renderer/utils/index.ts
            TransactionDetailsHeader.watch(tx) OK                       renderer/pages/TransactionDetails/components/TransactionDetailsHeader.vue


        BaseTransaction.updateTransactionKey FIXED                  renderer/components/Transaction/Create/BaseTransaction/BaseTransaction.vue

        useTransactionAudit.signatureKey() FIXED                    renderer/composables/useTransactionAudit.ts

        ExportTransactionsModal.handleExport() FIXED                renderer/components/ExternalSigning/ExportTransactionsModal.vue

        TransactionBrowserEntry.make() OK                           renderer/components/ExternalSigning/TransactionBrowser/TransactionBrowserEntry.ts

        filterTransactionFileItemsToBeSigned() OK                   shared/utils/transactionFile.ts

        TransactionBrowserKeySection.updateSignatureKeyObject() OK  renderer/components/ExternalSigning/TransactionBrowser/TransactionBrowserKeySection.vue

        TransactionDetails.fetchTransaction() FIXED                 renderer/pages/TransactionDetails/TransactionDetails.vue

        collectMissingSignerKeys() OK                               shared/utils/transactionFile.ts

OK means code is already protected from bubbling errors.
FIXED means code is updated by this PR.

Related issue(s):

Prerequisite for #2552

Notes for reviewer:

M   front-end/src/renderer/utils/transactionSignatureModels/transaction.model.ts
    # TransactionBaseModel.computeSignatureKey() now propagates errors

M   front-end/src/renderer/components/ExternalSigning/ExportTransactionsModal.vue
M   front-end/src/renderer/components/Transaction/Create/BaseTransaction/BaseTransaction.vue
M   front-end/src/renderer/composables/useTransactionAudit.ts
M   front-end/src/renderer/pages/TransactionDetails/TransactionDetails.vue
    # Now processes errors bubbling from computeSignatureKey()

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.95%. Comparing base (d2c3e78) to head (3f4317d).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2607   +/-   ##
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  Coverage   99.95%   99.95%           
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  Files         183      183           
  Lines        7410     7410           
  Branches     1478     1478           
=======================================
  Hits         7407     7407           
  Misses          3        3           

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[Copilot]

Pull request overview

This PR updates the renderer transaction signature audit flow so that TransactionBaseModel.computeSignatureKey() no longer swallows mirror-node / cache lookup failures, enabling upstream code to detect and react to signature-key computation errors.

Changes:

• Make TransactionBaseModel.computeSignatureKey() rethrow lookup errors after logging.
• Update multiple callers to wrap computeSignatureKey() in try/catch and apply fallbacks when it fails.
• Adjust export filtering logic for “external signer only” flows to tolerate signature-key computation failures.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
front-end/src/renderer/utils/transactionSignatureModels/transaction.model.ts	Stops swallowing lookup exceptions and rethrows them so callers can handle failures.
front-end/src/renderer/pages/TransactionDetails/TransactionDetails.vue	Wraps signature-audit computation in try/catch and clears the audit on failure.
front-end/src/renderer/composables/useTransactionAudit.ts	Wraps signature-audit computation in try/catch and returns null on failure.
front-end/src/renderer/components/Transaction/Create/BaseTransaction/BaseTransaction.vue	Wraps transaction key computation in try/catch and falls back when it fails.
front-end/src/renderer/components/ExternalSigning/ExportTransactionsModal.vue	Adds try/catch around external-transaction filtering based on signature audit.

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[svienot]

LGTM