feat:implement sponsor review dashboard.

[Ekene001]

closes #85

Add sponsor review dashboard for project owners to manage submissions.

• Approve, reject, and request revision actions
• Optimistic UI updates for instant feedback
• Support multiple submissions with contributor, milestone, and timestamp display
• Deterministic date formatting for consistent rendering
• Responsive layout with proper mobile button wrapping

Summary by CodeRabbit

• New Features

  • Added a sponsor review dashboard showing submissions with contributor avatar, name, time, optional milestone, status badges, and actions to Approve, Reject, or Request Revision; actions update the UI optimistically per item and roll back if an action fails.

• Chores

  • Updated project dependencies and development tooling versions to keep builds and tests up to date.