Modularize and streamline billing templates; replace _billing_form.html with reusable modals and shared partials, and update styles and interactions for consistency and clarity. billing, feature management, and forms

Refactored club detail templates to modularize common UI components. Standardized layout, interactions, and styles across admin, billing, and feature cards for consistency and reusability.

billing/services/dues.py

@@ -114,7 +114,7 @@ def waive(due: Due, *, note: str = "") -> Due:
     return due
 
 
-def owing_dues(today: date | None = None):
+def owing_dues():
     return Due.objects.filter(status__in=Due.OWING)