Add "All" prospects view and refine filtering logic

Introduced a new "All" prospects page for admins to view and manage all prospects. Removed unused "Users" list and related logic from code. Updated filters to support the new "All" state and adjusted navigation to include the new page.

FoodsharingSiegen.Server/Pages/Prospects.razor.cs

@@ -36,11 +36,6 @@ namespace FoodsharingSiegen.Server.Pages
         /// </summary>
         private List<Prospect>? ProspectList { get; set; }
 
-        /// <summary>
-        ///     Gets or sets the value of the users (ab)
-        /// </summary>
-        private List<User>? Users { get; set; }
-
         #endregion
 
         #region Override InitializeDataAsync
@@ -50,11 +45,6 @@ namespace FoodsharingSiegen.Server.Pages
         {
             // Load prospects
             await LoadProspects();
-
-            // Load users
-            var getUsersR = await UserService.GetUsersAsync();
-            if (getUsersR.Success)
-                Users = getUsersR.Data;
         }
 
         #endregion