VSN-2656 refactor(admin-config): migrate agent-role + email + notification tables to shadcn unified design

• Top-level shells (AgentRoleView, AgentContent, EmailManagementPage) migrated from MUI Tabs to shadcn/Tailwind tabs with Lucide icons
• All tables converted to unified CSS grid design with #DBD7F9 purple header, rounded-2xl rows, colored left border:
  • Agent table (collaborateurs)
  • Equipe table
  • Role table (with expandable modules panel)
  • Connection history table
  • Notification table
  • Email templates / automations / history tables
• Container views (collaborators-content, equipe-list-view, role-content, notification-main-view) migrated MUI Box/Stack to flex divs and shadcn TableControlBar/TabsCustom/TablePagination
• Action buttons replaced with Lucide icons + neo-shadow hover states

Closes VSN-2656