🛡️ Sentinel: Add security middleware to FastAPI app

[lgcorzo]

🛡️ Sentinel: [Security Enhancement]

Vulnerability: The FastAPI application lacked CORSMiddleware and TrustedHostMiddleware, making it susceptible to cross-origin attacks and Host header injection if exposed publicly.
Fix: Added CORSMiddleware and TrustedHostMiddleware with configurable allowed origins and hosts (defaulting to *).
Verification:

• Validated middleware injection via script.
• Confirmed strict schema validation and existing exception handling remains intact.
• Updated .jules/sentinel.md with security learning.

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PR created automatically by Jules for task 11180972438838537266 started by @lgcorzo

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