chore: settings/developer - remove pages router and use app router

[hbjORbj]

What does this PR do?

• Fixes CAL-4404
• remove pages router and use app router for all pages in settings/developer
• remove env vars not needed anymore as a result

Mandatory Tasks (DO NOT REMOVE)

• I have self-reviewed the code (A decent size PR without self-review might be rejected).
• N/A - I have added a Docs issue here if this PR makes changes that would require a documentation change. If N/A, write N/A here and check the checkbox.
• I confirm automated tests are in place that prove my fix is effective or that my feature works.

How should this be tested?

• all settings/developer/**/* pages must work as expected

[linear]

CAL-4404 `settings/developer` - Use app router and remove pages router

[graphite-app]

Graphite Automations

"Add consumer team as reviewer" took an action on this PR • (09/24/24)

1 reviewer was added to this PR based on Keith Williams's automation.

"Add platform team as reviewer" took an action on this PR • (09/24/24)

1 reviewer was added to this PR based on Keith Williams's automation.

"Add foundation team as reviewer" took an action on this PR • (09/24/24)

1 reviewer was added to this PR based on Keith Williams's automation.

[github-actions]

E2E results are ready!

• Workflow #36846.1 latest results

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2 Skipped Deployments

Name	Status	Preview	Comments	Updated (UTC)
cal	⬜️ Ignored (Inspect)	Visit Preview		Nov 5, 2024 2:00am
calcom-web-canary	⬜️ Ignored (Inspect)	Visit Preview		Nov 5, 2024 2:00am

[github-actions]

This PR is being marked as stale due to inactivity.