[Feature]: Easy seed accessor across the entire codebase

[adamamer20]

🤔 Problem Description

Users should use a single seed across the entire database and we should make it easy to change it and view it anywhere.
Currently is implemented in ModelDF, but it's not exposed as a property (also AgentsDF and AgentSetPolars should be able to access it)

💡 Proposed Solution

Create a property for all public classes (maybe a Seed Mixin?).

🔄 Alternatives Considered

No response

➕ Additional Context

No response