Replace deprecated event hooks with lifecycle handler

[vishesh10]

User description

Background

This PR replaces the deprecated @app.on_event hooks with lifecycle handler.
Addresses #7947

Changes 🏗️

• Updated the ws_api.py file to have lifecycle handlers instead of on_event hooks.

PR Quality Scorecard ✨

• Have you used the PR description template?   +2 pts
• Is your pull request atomic, focusing on a single change?   +5 pts
• Have you linked the GitHub issue(s) that this PR addresses?   +5 pts
• Have you documented your changes clearly and comprehensively?   +5 pts
• Have you changed or added a feature?   -4 pts
  • Have you added/updated corresponding documentation?   +4 pts
  • Have you added/updated corresponding integration tests?   +5 pts
• Have you changed the behavior of AutoGPT?   -5 pts
  • Have you also run agbenchmark to verify that these changes do not regress performance?   +10 pts

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PR Reviewer Guide 🔍

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Key issues to review Potential Race Condition The lifespan function creates an asyncio task for event_broadcaster, but doesn't ensure it's properly cancelled on shutdown. This could lead to a race condition or resource leaks.

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[aarushik93]

Thanks for your contribution - can you please run the linter?

[Swiftyos]

To run the linter you do:

poetry format in autogpt_sever folder

[vishesh10]

Thanks for considering this PR @aarushik93 @Swiftyos. The same is done.