#84 UI: Invitations Management Page

Create Invitations management page. Component: api/ui/templates/components/admin_invitations/ Files: - admin_invitations.html - admin_invitations.css - admin_invitations.js URL: #/admin/invitations Features: - Send Invitation section: - Email input (with domain validation if restricted) - Role selector dropdown - Custom message textarea (optional) - Send button - Success/error feedback - Pending Invitations table: - Columns: Email, Role, Invited By, Sent, Expires, Status, Actions - Status badges: pending, expired, cancelled - Actions: Resend, Cancel - Resend counter display - Invitation History: - Toggle to show accepted/cancelled - Accepted date - User link for accepted invitations Statistics: - Pending count - Accepted this month - Expired this month - Conversion rate With ultra attention to details and correctness. Before closing: write comment summarizing implementation with screenshot.