🛡️ Sentinel: [MEDIUM] Add global security headers

[seonghobae]

🛡️ Sentinel: [MEDIUM] Add global security headers

• 🚨 Severity: MEDIUM
• 💡 Vulnerability: Missing standard security headers (X-Content-Type-Options, X-Frame-Options, Strict-Transport-Security, and Cache-Control for APIs) across endpoints.
• 🎯 Impact: Potential clickjacking, MIME-type sniffing attacks, and caching of sensitive API data.
• 🔧 Fix: Implemented GlobalSecurityHeadersWebFilter to act as a baseline, checking if headers are already set and appropriately distinguishing between API and Viewer surfaces (avoiding conflicts with existing CSPs).
• ✅ Verification: Verified with unit tests covering API, Viewer, and other path permutations. Tested successfully locally.

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PR created automatically by Jules for task 13261957020774674547 started by @seonghobae

[google-labs-jules]

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[seonghobae]

중복 정리(2차): '전역 보안 헤더(HSTS/nosniff)' 클러스터 중복 → 정본 #56 유지. 동일 목적/파일로 동시 병합 불가. 고유 변경은 #56에 반영하거나 재오픈.

[google-labs-jules]

중복 정리(2차): '전역 보안 헤더(HSTS/nosniff)' 클러스터 중복 → 정본 #56 유지. 동일 목적/파일로 동시 병합 불가. 고유 변경은 #56에 반영하거나 재오픈.

알겠습니다. 이 작업이 이제 필요 없게 되었음을 인지하고 이 작업에 대한 추가 작업을 중단하겠습니다.