feat: add webhook management UI and BeforeNodeDeletedEvent support

Added comprehensive webhook management capabilities including:

Webhook Client & API:
- Added WebhooksClient for Nextcloud webhooks API integration
- Create, list, update, and delete webhooks programmatically
- Support for event filters in webhook registration

Webhook Presets:
- Added preset system for common webhook configurations
- notes_sync: BeforeNodeDeletedEvent for Notes file operations
- calendar_sync: Calendar events (create, update, delete)
- deck_sync: Deck card operations
- files_sync: File system changes
- forms_sync: Form submissions (conditional)
- Filter presets by installed apps

Admin UI:
- Added multi-pane app view with tabs (User Info, Vector Sync, Webhooks)
- Webhooks tab for admin users only
- Enable/disable preset webhooks via UI
- View currently registered webhooks
- Uses htmx for dynamic loading and Alpine.js for tab state
- Admin permission checking via OCS API

CLI Improvements:
- Refactored CLI to separate module (cli.py)
- Updated entry point in pyproject.toml

BeforeNodeDeletedEvent Fix:
- Updated ADR-010 to document NodeDeletedEvent issue
- BeforeNodeDeletedEvent includes node.id before deletion
- NodeDeletedEvent lacks node.id (file already deleted)
- Implemented per Nextcloud maintainer recommendation

Testing:
- Added comprehensive webhook client tests
- Added webhook preset filtering tests
- Added admin permission tests

Configuration:
- Updated docker-compose.yml Qdrant settings

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

nextcloud_mcp_server/auth/permissions.py

@@ -0,0 +1,54 @@
+"""Permission checking utilities for Nextcloud admin operations."""
+
+import logging
+
+from httpx import AsyncClient
+from starlette.requests import Request
+
+from nextcloud_mcp_server.client.users import UsersClient
+
+logger = logging.getLogger(__name__)
+
+
+async def is_nextcloud_admin(request: Request, http_client: AsyncClient) -> bool:
+    """Check if the authenticated user is a Nextcloud administrator.
+
+    This function extracts the username from the session/request context
+    and checks if the user is a member of the "admin" group in Nextcloud.
+
+    Args:
+        request: Starlette request object with authenticated user
+        http_client: Authenticated HTTP client for Nextcloud API calls
+
+    Returns:
+        True if user is admin, False otherwise
+
+    Example:
+        ```python
+        if await is_nextcloud_admin(request, http_client):
+            # Show admin-only features
+            pass
+        ```
+    """
+    try:
+        # Extract username from authenticated session
+        username = request.user.display_name
+        if not username:
+            logger.warning("No username found in authenticated session")
+            return False
+
+        # Query Nextcloud for user's group memberships
+        users_client = UsersClient(http_client, username)
+        user_groups = await users_client.get_user_groups(username)
+
+        # Check if user is in the admin group
+        is_admin = "admin" in user_groups
+        logger.debug(
+            f"Admin check for user '{username}': {is_admin} (groups: {user_groups})"
+        )
+
+        return is_admin
+
+    except Exception as e:
+        logger.error(f"Error checking admin permissions: {e}", exc_info=True)
+        return False