🛡️ Sentinel: [HIGH] Fix Slow Read DoS vulnerability (Missing Write Deadline)

[tejjasdev]

🚨 Severity: HIGH
💡 Vulnerability: The HTTP server lacked a write deadline (write timeout) for default responses, making it vulnerable to Slow Read Denial of Service (DoS) attacks.
🎯 Impact: An attacker could intentionally read response bytes slowly, holding open server connections indefinitely and potentially exhausting server resources.
🔧 Fix: unconditionally invoke SetWriteDeadline via http.NewResponseController(w) for both standard responses and CORS preflight requests.
✅ Verification: Covered by existing server test suite; confirmed via make check.

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PR created automatically by Jules for task 4002513079532924682 started by @tejjasdev

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