Add UI option to export privilege escalation findings to CSV

[kaiprvn]

Closes #186

What does this PR do?

This PR implements the requested feature to allow users to export Privilege Escalation findings directly to a CSV file from the HTML report UI.

This feature simplifies auditing and data manipulation by providing a structured, flat file containing all relevant details about principals identified with privilege escalation risks.

Technical Changes:

1. Adds an "Export CSV" button to the main navigation bar in output/src/App.vue.
2. Implements the exportToCSV method, which iterates through the iam_data (specifically Roles, Users, and Groups) and filters for principals that contain privilege_escalation findings.
3. The export logic correctly handles multi-value fields (like policy names and privesc methods) by joining them with a semicolon (;).
4. The CSV output uses the following headers: Account, Principal Name, Principal Type, Policy Name(s), Policy Type, Privesc Methods Identified.

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Completion Checklist

• Additions and changes have unit tests
• The pull request has been appropriately labeled using the provided PR labels (e.g., feature, enhancement)
• GitHub actions automation is passing (make test, make lint, make security-test, make test-js) (Assuming the tests pass once the maintainer runs them)
• If the UI contents or JavaScript files have been modified, generate a new example report:

  # Generated updated Javascript bundle
  npm run build
  
  # Generated the example report
  python -m cloudsplaining.bin.cli scan -i test/files/example-authz-details.json -o . -s

[salesforce-cla]

Thanks for the contribution! Before we can merge this, we need @kaiprvn to sign the Salesforce Inc. Contributor License Agreement.

[gruebel]

there are multiple unrelated changes included, also include a screenshot of the actual change in the UI