Deprecate root PII scrubber

[BojayL]

Summary

• Replace the root scrubber.py implementation with a deprecation reference to the canonical AI service scrubber.
• Update the root PII regression test to exercise PIIScrubberService from app/ai-service/services/pii_scrubber.py.
• Align root PII fixtures with the canonical scrubber token names and supported ID pattern.

Fixes #112

Testing

• Python 3.10 venv with app/ai-service/requirements.txt installed
• PYTHONPATH=app/ai-service python -m pytest tests/test_pii_scrubber.py app/ai-service/tests/test_pii_scrubber.py app/ai-service/tests/test_pii_regression.py -q