Add ReadLog method to headscale integration container for log
inspection. Split SSH check mode tests into CLI and OIDC variants
and add comprehensive test coverage:
- TestSSHOneUserToOneCheckModeCLI: basic check mode with CLI approval
- TestSSHOneUserToOneCheckModeOIDC: check mode with OIDC approval
- TestSSHCheckModeUnapprovedTimeout: rejection on cache expiry
- TestSSHCheckModeCheckPeriodCLI: session expiry and re-auth
- TestSSHCheckModeAutoApprove: auto-approval within check period
- TestSSHCheckModeNegativeCLI: explicit rejection via CLI
Update existing integration tests to use headscale auth register.
Updates #1850
3db0a483ed