Fix incorrect currency symbol in distance rate update changelog message

[mukhrr]

Explanation of Change

The rate-creation changelog message formats the raw amount client-side with Intl (convertAmountToDisplayString), but the rate-update message rendered backend-preformatted oldValue/newValue strings verbatim, so currencies like ARS showed the currency-list symbol (AR$1,40) instead of the Intl format (ARS 1.40).

The backend now sends raw oldRate/newRate (in cents) and currency in the POLICYCHANGELOG_UPDATE_CUSTOM_UNIT_RATE original message. This PR makes getWorkspaceCustomUnitRateUpdatedMessage prefer those raw fields and format them with convertAmountToDisplayString, the same helper the creation message uses, so both messages agree for every currency. The legacy oldValue/newValue string branch is kept as a fallback for old cached actions.

Fixed Issues

$ #93144
PROPOSAL: #93144 (comment)

Tests

Precondition: a workspace whose currency is not USD (e.g. ARS) with Distance rates enabled.

1. Go to Workspaces > [workspace] > Distance rates.
2. Click "Add rate" and create a rate, e.g. 1.30.
3. Open the newly created rate and update the amount, e.g. to 1.40.
4. Go to the workspace #Admins room.
5. Verify the "changed the rate of the distance rate..." message shows the amount in the same format as the rate-creation message (e.g. ARS 1.40 (previously ARS 1.30)), not the currency symbol (AR$1,40).

• Verify that no errors appear in the JS console

Offline tests

QA Steps

Same as Tests.

• Verify that no errors appear in the JS console

PR Author Checklist

• I linked the correct issue in the ### Fixed Issues section above
• I wrote clear testing steps that cover the changes made in this PR
  • I added steps for local testing in the Tests section
  • I added steps for the expected offline behavior in the Offline steps section
  • I added steps for Staging and/or Production testing in the QA steps section
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  • I turned off my network connection and tested it while offline to ensure it matches the expected behavior (i.e. verify the default avatar icon is displayed if app is offline)
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• I included screenshots or videos for tests on all platforms
• I ran the tests on all platforms & verified they passed on:
  • Android: Native
  • Android: mWeb Chrome
  • iOS: Native
  • iOS: mWeb Safari
  • MacOS: Chrome / Safari
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Screenshots/Videos

Android: Native

IOS_app.mp4

Android: mWeb Chrome

android_web.mp4

iOS: Native

IOS_app.mp4

iOS: mWeb Safari

IOS_web.mp4

MacOS: Chrome / Safari

93144-web.mp4

[melvin-bot]

@truph01 Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

[truph01]

@mkhutornyi It looks like you are reviewer of this one, right?

[mkhutornyi]

@mkhutornyi It looks like you are reviewer of this one, right?

right

[truph01]

@garrettmknight Could you assign @mkhutornyi and unassign me?