* fix: Handle circular references in spend tracking metadata JSON serialization
- Fixes issue #12634 where circular references in metadata caused
ValueError: Circular reference detected when logging spend data
- Adds _safe_json_dumps() function that detects and handles circular
references by replacing them with placeholder strings
- Maintains full functionality for normal objects while preventing
crashes from circular references
- Adds comprehensive tests for circular reference handling
- Critical fix for v1.74.3 stable release
* fix: Replace bare except clauses with specific Exception handling
- Fixes E722 linting errors in _safe_json_dumps function
- Maintains same error handling behavior while following best practices
- All tests continue to pass
* refactor: Use existing safe_dumps utility instead of custom implementation
- Replace custom _safe_json_dumps() with existing safe_dumps() from litellm_core_utils
- Remove duplicate code and leverage existing circular reference handling
- Update tests to use safe_dumps function
- Maintains same functionality while reducing code duplication
- All tests continue to pass
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