feat: Merge Atomizer-Field neural network module into main repository

Permanently integrates the Atomizer-Field GNN surrogate system:
- neural_models/: Graph Neural Network for FEA field prediction
- batch_parser.py: Parse training data from FEA exports
- train.py: Neural network training pipeline
- predict.py: Inference engine for fast predictions

This enables 600x-2200x speedup over traditional FEA by replacing
expensive simulations with millisecond neural network predictions.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

atomizer-field/.gitignore

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+# Python
+__pycache__/
+*.py[cod]
+*$py.class
+*.so
+.Python
+env/
+venv/
+ENV/
+*.egg-info/
+dist/
+build/
+
+# Jupyter Notebooks
+.ipynb_checkpoints/
+*.ipynb
+
+# IDEs
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Data files (large)
+*.op2
+*.bdf
+*.dat
+*.f06
+*.pch
+*.h5
+*.hdf5
+
+# Training data
+training_data/
+checkpoints/
+runs/
+logs/
+
+# Test outputs
+test_case_*/
+visualization_images/
+
+# Temporary files
+*.tmp
+*.log
+*.bak
+*.orig
+
+# Environment
+atomizer_env/
+.conda/