feat: add public profiles list endpoint with search and pagination

- Add new /profiles/ endpoint for listing user profiles
- Support search by username/display name with ordering options
- Include pagination with configurable page size (max 100)
- Add comprehensive OpenAPI schema documentation
- Refactor passkey authentication state management in MFA flow
- Update URL routing and imports for new list_profiles view

This enables user discovery, leaderboards, and friend-finding features
with a publicly accessible, well-documented API endpoint.

backend/apps/api/v1/accounts/views.py

@@ -823,6 +823,119 @@ def check_user_deletion_eligibility(request, user_id):
         )
 
 
+# === PUBLIC PROFILE LIST ENDPOINT ===
+
+
+@extend_schema(
+    operation_id="list_profiles",
+    summary="List user profiles with search and pagination",
+    description=(
+        "Returns a paginated list of public user profiles. "
+        "Supports search by username or display name, and filtering by various criteria. "
+        "This endpoint is used for user discovery, leaderboards, and friend finding."
+    ),
+    parameters=[
+        OpenApiParameter(
+            name="search",
+            type=OpenApiTypes.STR,
+            location=OpenApiParameter.QUERY,
+            description="Search term for username or display name",
+        ),
+        OpenApiParameter(
+            name="ordering",
+            type=OpenApiTypes.STR,
+            location=OpenApiParameter.QUERY,
+            description="Order by field: date_joined, -date_joined, username, -username",
+        ),
+        OpenApiParameter(
+            name="page",
+            type=OpenApiTypes.INT,
+            location=OpenApiParameter.QUERY,
+            description="Page number for pagination",
+        ),
+        OpenApiParameter(
+            name="page_size",
+            type=OpenApiTypes.INT,
+            location=OpenApiParameter.QUERY,
+            description="Number of results per page (max 100)",
+        ),
+    ],
+    responses={
+        200: {
+            "description": "Paginated list of public profiles",
+            "example": {
+                "count": 150,
+                "next": "https://api.thrillwiki.com/api/v1/accounts/profiles/?page=2",
+                "previous": None,
+                "results": [
+                    {
+                        "user_id": "uuid-1",
+                        "username": "thrillseeker",
+                        "date_joined": "2024-01-01T00:00:00Z",
+                        "role": "USER",
+                        "profile": {
+                            "profile_id": "uuid-profile",
+                            "display_name": "Thrill Seeker",
+                            "avatar_url": "https://example.com/avatar.jpg",
+                            "bio": "Coaster enthusiast!",
+                            "total_credits": 150,
+                        },
+                    }
+                ],
+            },
+        },
+    },
+    tags=["User Profile"],
+)
+@api_view(["GET"])
+@permission_classes([AllowAny])
+def list_profiles(request):
+    """
+    List public user profiles with search and pagination.
+    
+    This endpoint provides the missing /accounts/profiles/ list endpoint
+    that the frontend expects for user discovery features.
+    """
+    from django.db.models import Q
+    from rest_framework.pagination import PageNumberPagination
+    
+    # Base queryset: only active users with public profiles
+    queryset = User.objects.filter(
+        is_active=True,
+    ).select_related("profile").order_by("-date_joined")
+    
+    # Search filter
+    search = request.query_params.get("search", "").strip()
+    if search:
+        queryset = queryset.filter(
+            Q(username__icontains=search) |
+            Q(profile__display_name__icontains=search)
+        )
+    
+    # Ordering
+    ordering = request.query_params.get("ordering", "-date_joined")
+    valid_orderings = ["date_joined", "-date_joined", "username", "-username"]
+    if ordering in valid_orderings:
+        queryset = queryset.order_by(ordering)
+    
+    # Pagination
+    class ProfilePagination(PageNumberPagination):
+        page_size = 20
+        page_size_query_param = "page_size"
+        max_page_size = 100
+    
+    paginator = ProfilePagination()
+    page = paginator.paginate_queryset(queryset, request)
+    
+    if page is not None:
+        serializer = PublicUserSerializer(page, many=True)
+        return paginator.get_paginated_response(serializer.data)
+    
+    # Fallback if pagination fails
+    serializer = PublicUserSerializer(queryset[:20], many=True)
+    return Response(serializer.data, status=status.HTTP_200_OK)
+
+
 # === USER PROFILE ENDPOINTS ===