[Phase 6] Build GroupDetail page — Members tab

[MohamedRamadanSaudi]

Task

Create frontend/src/pages/GroupDetail/tabs/MembersTab/.

Components

• MemberRow — avatar, name, email, role badge; admin sees role dropdown + remove button
• InviteMemberForm — email input + Send Invite button
• PendingInvitations — list of pending invites with cancel action (admin/mod only)

Behavior

• Role changes call updateMemberRole
• Remove calls removeMember
• Owner row has no remove/downgrade option