fix(agents-api): Fix updating task execution

[HamadaSalhab]

[!IMPORTANT] Improves task execution updates by encoding task tokens with metadata and enhancing error handling in raise_complete_async.py and update_execution.py.

• Behavior:
  • In raise_complete_async.py, task tokens are now base64 encoded and include metadata with activity, run, and workflow IDs.
  • In update_execution.py, added error handling for stopping and resuming executions, using metadata for async activity handle retrieval.
• Database Queries:
  • In get_paused_execution_token.py, query updated to include metadata and sort by created_at with a limit of 1.
• Error Handling:
  • Added try-except blocks in update_execution.py to handle exceptions when stopping or resuming executions.

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