Find and process next batch directory

[antonleykin]

This PR introduces batch_processor.sh, a script to automate the distributed execution of gfan commands across BATCH-i subdirectories.

The script ensures that:

• Only one gfan process runs per batch at a time, using processing files.
• Completed batches are marked with done files, preventing re-execution.
• Available batches are automatically identified and processed, streamlining large-scale computations.

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[cursor]

Cursor Agent can help with this pull request. Just @cursor in comments and I'll start working on changes in this branch.
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