v1.6.0

Changelog

• 3602f27 Add update_account and update_container tools
• df32d3c Bump version to 1.5.9
• 5ce1bdc feat: OAuth-authenticated users also use SA token source when S2S configured
• d90a569 feat: add S2S API key branch to auth middleware
• 41752d5 feat: add service account config fields
• a97f85d feat: add service account token source and context helpers
• 0f2003c feat: getClient checks SA token source before OAuth token
• 4aa3d37 feat: wire service account S2S mode at startup
• 60e0375 fix: set ExpiresAt on SA TokenInfo to avoid zero-value expiry
• bb3611a release: bump to v1.6.0 — S2S service account auth