refactor: extracted pure functions from background effects handler and controller [WPB-23253]

[zskhan]

WPB-23253 Bring Blurred Background Spike into Webapp Edge

Summary

• What did I change and why?
  Extracted pure functions from background effects handler and also from the background effects controller and wrote few more tests
• Risks and how to roll out / roll back (e.g. feature flags):

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Security Checklist (required)

• External inputs are validated & sanitized on client and/or server where applicable.
• API responses are validated; unexpected shapes are handled safely (fallbacks or errors).
• No unsafe HTML is rendered; if unavoidable, sanitization is applied and documented where it happens.
• Injection risks (XSS/SQL/command) are prevented via safe APIs and/or escaping.

Accessibility (required)

• I have read and this PR upholds our Accessibility Best Practices.

Standards Acknowledgement (required)

• I have read and this PR upholds our Coding Standards and Tech Radar Choices.

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Screenshots or demo (if the user interface changed)

Notes for reviewers

• Trade-offs:
• Follow-ups (linked issues):
• Linked PRs (e.g. web-packages):

[github-actions]

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🧪 Playwright Test Summary

• ✅ Passed: 12
• ❌ Failed: 0
• ⏭ Skipped: 0
• 🔁 Flaky: 2
• 📊 Total: 14
• ⏱ Total Runtime: 780.1s (~ 13 min 0 sec)

specs/CriticalFlow/groupVideoCall-TC-8637.spec.ts (❌ 0 failed, ⚠️ 1 flaky)

• ⚠️ Group Video call (tags: TC-8637, crit-flow-web)

specs/CriticalFlow/oneOnOneCall-TC-8754.spec.ts (❌ 0 failed, ⚠️ 1 flaky)

• ⚠️ 1:1 Video call with device switch and screenshare (tags: TC-8754, crit-flow-web)

[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud