Fix initialization infinite loop and NumPy ndarray.__repr__ error

[alexlib]

Summary

• Fixed infinite loop during experiment initialization by properly handling PTVCore imports
• Fixed NumPy ndarray.repr error by using PTVCoreBridge directly
• Added additional logging and error handling for better debugging
• Added test script to validate the initialization process

Test plan

1. Run python test_app.py to test the initialization process
2. Open the UI with python -m pyptv.ui.app --exp-path tests/test_cavity
3. Initialize an experiment using File > Open Experiment

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