Implement Soroban Finding Ownership Assignment

[mijinummi]

🧠 Concept

Assign findings to responsible modules or teams.

⚠️ Problem

Large projects struggle to triage findings efficiently.

📁 Implementation Scope

• src/findings/ownership/stellar/

✅ Requirements

• Map findings to ownership rules
• Generate assignment metadata
• Support custom ownership mappings

🎯 Acceptance Criteria

• Ownership assignment implemented
• Findings mapped correctly