CCM-13492: initial spinner

[alexnuttall]

Description

PR to add a page level spinner when the initial render is pending. This is only displayed when viewing the page within 20s of template creation.

Playwright tests cover the spinner, but not spinner timeout. This will be covered in e2e and/or system tests.

Polling works by calling router.refresh which rerenders server components but preserves client state. I think this might also work for the per-tab renders

Context

Type of changes

• Refactoring (non-breaking change)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would change existing functionality)
• Bug fix (non-breaking change which fixes an issue)

Checklist

• I am familiar with the contributing guidelines
• I have followed the code style of the project
• I have added tests to cover my changes
• I have updated the documentation accordingly
• This PR is a result of pair or mob programming
• If I have used the 'skip-trivy-package' label I have done so responsibly and in the knowledge that this is being fixed as part of a separate ticket/PR.

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• I confirm that neither PII/PID nor sensitive data are included in this PR and the codebase changes.