[support] Replace hardcoded countervalues URL with value from env var

[ghost]

📝 Description

For some bad reason, the URL of the countervalues backend was hardcoded in a couple places in the code.
This PR just replaces these with the value from the env var.

Additionally it makes Hedera use the countervalue API in Live instead of directly hitting the countervalue backend.

❓ Context

• JIRA or GitHub link: https://ledgerhq.atlassian.net/browse/LIVE-10620

✅ Checklist

Pull Requests must pass the CI and be code reviewed. Set as Draft if the PR is not ready.

• npx changeset was attached.
• Covered by automatic tests.
• Impact of the changes: Hedera uses the countervalue API

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🧐 Checklist for the PR Reviewers

• The code aligns with the requirements described in the linked JIRA or GitHub issue.
• The PR description clearly documents the changes made and explains any technical trade-offs or design decisions.
• There are no undocumented trade-offs, technical debt, or maintainability issues.
• The PR has been tested thoroughly, and any potential edge cases have been considered and handled.
• Any new dependencies have been justified and documented.
• Performance considerations have been taken into account. (changes have been profiled or benchmarked if necessary)

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[gre]

we need to make getEnv called lazily, otherwise all is good

[ghost]

@gre Ready for review, let me know if this is OK regarding cvs API.