🛡️ Sentinel: [HIGH] Add CORS and TrustedHost middleware

[lgcorzo]

🚨 Severity: HIGH
💡 Vulnerability: Overly permissive CORS configuration and Missing TrustedHostMiddleware.
🎯 Impact:
- Without CORS, legitimate cross-origin requests are blocked by browsers.
- Without TrustedHostMiddleware, the application is vulnerable to Host Header attacks.
🔧 Fix:
- Added CORSMiddleware and TrustedHostMiddleware to src/regression_model_template/controller/kafka_app.py.
- Configured them via ALLOWED_ORIGINS and ALLOWED_HOSTS environment variables.
✅ Verification:
- Added tests/controller/test_kafka_app_middleware.py which verifies that the middlewares are present and correctly configured.

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PR created automatically by Jules for task 15023835416815364786 started by @lgcorzo

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