add optional file handler to get_logger

[kirito201922]

Adds optional file logging support to get_logger based on the POLYMARKET_LOG_FILE environment variable. When set, logs are written both to stdout and to the specified file.

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Note

Enables file-based logging alongside existing stdout logging in get_logger.

• When POLYMARKET_LOG_FILE is set, adds a FileHandler with the same formatter, in addition to the StreamHandler
• Renames handler to stream_handler for clarity; otherwise preserves logging level, formatter, and early-return behavior

^{Written by Cursor Bugbot for commit a800d40. This will update automatically on new commits. Configure here.}

[cursor]

Diff markers committed as actual Python source code

The file agents/logging_utils.py contains raw diff/patch output instead of valid Python code. The file includes diff markers like @@, lines prefixed with - (removed lines), and lines prefixed with + (added lines). This is not valid Python syntax and will cause a SyntaxError when imported. It appears a diff/patch file was accidentally committed instead of the actual implementation.