refactor(webapp): rename startup feature flags to startup feature toggles [WPB-23826]

[screendriver]

WPB-23826 [Web] Optimize websocket implementation

Pull Request

Summary

This change standardizes the startup surface on "feature toggles" terminology and keeps startup toggle behavior explicit and predictable at application boot. The expected outcome is clearer naming across the startup flow, easier reasoning about toggle state, and less ambiguity when discussing or extending startup-controlled behavior.

---

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.

---

Screenshots or demo (if the user interface changed)

Notes for reviewers

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

[sonarqubecloud]

Quality Gate passed

Issues
0 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

[github-actions]

🔗 Download Full Report Artifact

🧪 Playwright Test Summary

• ✅ Passed: 11
• ❌ Failed: 0
• ⏭ Skipped: 3
• 🔁 Flaky: 0
• 📊 Total: 14
• ⏱ Total Runtime: 84.1s (~ 1 min 24 sec)