[Frontend] [Feature] Create Next.js API route to fetch SPV Attestation history

[Tybravo]

🎯 Goal

Build a backend route to fetch historical attestations for the user's dashboard.

📋 Requirements

• Implement the feature as described in the goal.
• Ensure integration matches the architecture defined in SUMMARY_TYPESCRIPT.md.
• Handle relevant loading and error states gracefully.

🔧 Technical Scope

• Next.js API Routes

📂 Affected Path

frontend/app/api/attestations/route.ts

✅ Acceptance Criteria

• API returns valid JSON history.

🔗 PR Requirements

• PR description must include: Closes #[issue_id]