C-150: Pre-launch checklist sign-off (both owners)

**Owner:** @kh0ra  ·  **Reviewer:** @mehmethayirli
**Milestone:** M11 Launch

Audit closed, mainnet smoke + acceptance green, ToS/Privacy live, secrets rotated, monitoring on, rollback rehearsed.

**Acceptance criteria**
- Both owners sign off.

_Tracked in docs/MAINNET_ROADMAP.md (C-150)._