#50 Issue 50: [Docs] Comprehensive Security Model & Threat Map

[JerryIdoko]

Description:
Document the security assumptions of the protocol, including what happens if the Admin is compromised or if the Stellar network experiences downtime.

Acceptance Criteria:

[ ] Create SECURITY_MODEL.md.

[ ] List all trust assumptions and mitigation strategies for "God-mode" admin keys.
Labels: documentation, security