feat: Implement agent filtering by integrating a new API endpoint for filterable fields, introducing filter data models, and adding a dedicated filter sheet UI, alongside an updated profile icon.

lib/core/constants/api_constants.dart

@@ -16,6 +16,9 @@ class ApiConstants {
   static const String agents = '/agents';
   static const String agentTypes = '/agent-types';
 
+  // Profile fields
+  static const String filterableFields = '/profile-fields/filterable';
+
   // CMS
   static const String cmsPageLanding = '/cms/page/landing';
 }