SSO Phase 1 Task 7: logout revokes the SSO session

[ahmetabdullahgultekin]

Why: Logout must terminate the hub session and expire the cookie, or a stolen/leftover cookie keeps minting codes.

Done when:

• Modify the POST /auth/logout handler/service to revoke the SSO session in the store + expire the fv_sso cookie (max-age 0) when the flag is ON.
• Failing test first (extends the logout test): after logout the session is revoked and the response expires the cookie.

source: docs/SSO_APP_LAUNCHER_PHASE1_PLAN.md:78

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Migrated from docs/SSO_APP_LAUNCHER_PHASE1_PLAN.md (git history retains the original).