[AI] Add Soroban-specific prompt actions

[Atharv777]

Summary

Add prebuilt AI prompts for Soroban workflows.

Why this matters

Generic AI is not enough. Domain-specific prompts unlock real value.

Scope

• Generate contract
• Explain contract
• Generate tests
• Security review

Acceptance Criteria

• Prompts produce useful results
• Output can be inserted into editor
• UX is simple and intuitive

Files Involved

• pages/app/index.jsx
• components/*
• server/agent.py

Difficulty

Medium

Labels: ai soroban frontend