Handle cyclic references in exceptions

[alexmojaki]

Closes #1279

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Pull Request Overview

This PR adds handling for cyclic references in exception chains to prevent infinite recursion when canonicalizing exception tracebacks. The implementation tracks previously seen exceptions using their object IDs and displays <repeated exception> for cycles.

• Adds a seen parameter to track visited exceptions by ID
• Implements cycle detection before processing exception causes, contexts, and groups
• Adds comprehensive test coverage for cyclic exception scenarios

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
logfire/_internal/utils.py	Implements cycle detection logic in canonicalize_exception_traceback function
tests/test_canonicalize_exception.py	Adds test cases for cyclic exception cause and exception group scenarios