Implement pre-audit checklist for the current scope

[azat-hafizov]

Guide to ensure Tapio contracts meet standards and best practices before we go into the next audit

• Using industry-known libraries where possible (at least OZ)
• Avoid using inline assembly where possible
• Latest major Solidity version
• Document functions (at least external/public)
• #25
• Tapio security assumptions declared to auditors
• Intentionally negative tests to expect breaking if required
• Checks/effects/interactions pattern
• Basic fuzz testing (Foundry) and static analysis (Slither)