feat: implement notification recall authorization, delivery confirmation, and audit trail

[najeebullahii]

Closes #301

Overview

This PR implements the notification recall and delivery confirmation features for the hello-world contract (including complete state coverage and audit trails via Soroban events) and resolves strict linting errors on the frontend dashboard.

What's Changed

🔒 Contract Backend (contract/)

• State Updates (types.rs): Extended ScheduledNotification metadata to track delivery and recall states (delivered, delivered_at, recalled_by, recalled_at).
• Core Logic (lib.rs, autoshare_logic.rs): Implemented confirm_notification_delivery and recall_notification with strict sender/admin ownership checks.
• Audit Trail & Testing: Created NotificationDelivered/NotificationRecalled events and added 18 comprehensive tests using Soroban try_ method patterns.
• Code Style: Formatted the backend codebase using cargo fmt to comply with CI style enforcement.

💻 Frontend Dashboard (dashboard/)

• Lint Fixes (ActivityFeed.tsx, EventExplorerPage.tsx): Removed unused _nextAddress callback parameters from the wallet sync hooks to satisfy strict @typescript-eslint/no-unused-vars rules.

Verification Results

• Backend Tests: cargo test -p hello-world notification_test -- --nocapture 👉 Result: 18 passed; 0 failed
• Backend Style: Checked and passing via cargo fmt --check
• Frontend Lint: npm run lint 👉 Result: 0 errors, 0 warnings (Passed successfully)

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