Add missing NIP-29 group admin UI components #nip29

[rabble]

Problem

The NIP-29 implementation lacks UI components for comprehensive group management. While the underlying provider can handle admin events (9000-9009), there's no user interface to trigger these actions.

Missing Admin Features

Based on docs/relay_nip29_notes.md, the following admin actions need UI:

• Group Creation (Kind 9007)
• Add/Remove Users (Kind 9000/9001)
• Edit Group Metadata (Kind 9002)
• Delete Group (Kind 9008)
• Create Group Invites (Kind 9003)
• Set User Roles (Kind 9004)
• Delete Events (Kind 9005)
• Edit Events (Kind 9006)

Current State

• ✅ Can read and display group content
• ✅ Can send messages to groups
• ❌ Cannot manage group settings
• ❌ Cannot add/remove members
• ❌ Cannot create or delete groups

Impact

• Users cannot fully manage their NIP-29 groups
• Admin functionality is incomplete
• Reduces the utility of NIP-29 groups vs alternatives

Acceptance Criteria

• Admin panel/modal for group settings
• Member management interface
• Group creation workflow
• Permission-based UI (only show admin actions to admins)
• Error handling for failed admin actions

Files to Create/Modify

• Group admin components
• Member management components
• Group creation forms
• Permission checking hooks

Tags: #nip29