feat: implement CookingEngine and physical pipeline

[parisasachdeva07]

🔗 Related Issue

Closes #146

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📝 Summary of Changes

Implemented the CookingEngine heuristic logic to detect 5 distinct recipe steps (pasta, baking, omelette, etc.) based on objects and OCR text.

Added safety threshold alerts for high temperatures parsing both Fahrenheit and Celsius.

Created core/physical/physical_pipeline.py from scratch to serve as the main routing hub.

Registered the cooking engine inside the new pipeline to trigger when task_type == "cooking".

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🔍 Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📖 Documentation update
• 🧪 Test addition or improvement
• 🧹 Refactor / Code cleanup (no functional change)
• ⚙️ Build / CI / Chore

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🧪 How Was This Tested?

Ran the dedicated unit test suite for the engine, verifying tie-breakers and UnboundLocalError edge cases.
python -m unittest tests.unit.test_cooking_engine

# Example: commands run to test your changes
python -m pytest tests/unit/test_your_module.py -v

Test environment:

• OS: Windows 11
• Python version: 3.1.4
• Node version (if frontend):

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📸 Screenshots / Recordings (if applicable)

N/A - Backend pipeline and engine logic

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✅ Pre-Submission Checklist

• My branch is up to date with upstream/main
• My code follows the project's coding standards (Black, isort, flake8 pass)
• I have written / updated tests for my changes
• All existing tests pass (python -m pytest tests/)
• I have added docstrings and type hints to all new public functions
• I have updated relevant documentation (README, docs/, inline comments)
• My PR title follows the Conventional Commits format
• I have not committed any .env files, secrets, or model weights
• This PR addresses only the scope of the linked issue

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💬 Additional Notes for Reviewer

Note: The PhysicalPipeline class did not exist yet, so I created physical_pipeline.py to handle the routing. Future domain engines (like workout or hardware repair) can now easily be added to this pipeline's process method!