Remove user engagement and error tracking.

[jamesbiederbeck]

Description

Removes third-party tracking and error-reporting integrations from the app: Pulse (Schibsted) user engagement tracking and the Sentry SDK.

• Stripped Pulse init/tracking calls from index.html, Editor.js, SettingEmail.js, and AudioPlayer.js (page views, engagement clicks, file-upload events).
• Removed the Sentry SDK entirely: server-side init and FlaskIntegration/RqIntegration in main.py, set_user() calls in main.py and transcriber.py (which sent user emails to Sentry), the /debug-sentry test route, the client-side Sentry script block in index.html, the sentry-sdk dependency in requirements.txt, and unused env wiring in worker-settings.py and dotenv-example.
  Closes Remove User Tracking or Add Privacy Policy #254

Checklist:

• My code has been linted to follow the code style of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works subtractive only pr, nothing to test