🛡️ Sentinel: Add CORS and TrustedHost middleware for security hardening

[lgcorzo]

This PR adds CORSMiddleware and TrustedHostMiddleware to the regression_model_template application to mitigate potential Host Header Injection attacks and allow granular control over Cross-Origin Resource Sharing (CORS).

Changes:

• Imported CORSMiddleware and TrustedHostMiddleware in src/regression_model_template/controller/kafka_app.py.
• Added configuration for ALLOWED_ORIGINS and ALLOWED_HOSTS environment variables (defaulting to * for backward compatibility).
• Added middleware registration to the FastAPI app instance.
• Added tests/controller/test_kafka_app_middleware.py to verify the middleware configuration.

Verification:

• New test tests/controller/test_kafka_app_middleware.py passes.
• Full CI suite (poetry run invoke checks) passes.

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PR created automatically by Jules for task 16277937647812599225 started by @lgcorzo

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