Implement Soroban Contract Linting Rules

[mijinummi]

🧠 Concept

Create custom linting rules for Soroban contracts.

⚠️ Problem

Rust linters do not fully cover Soroban-specific issues.

📁 Implementation Scope

• rules/stellar/linting/

✅ Requirements

• Add Soroban-specific rules
• Integrate with analysis engine

🎯 Acceptance Criteria

• Linting rules implemented