fix(products): improve bulk category modal behavior and initialization

- Move default date initialization from form to view initial data
- Add checks for DOM elements existence before event listener attachment
- Handle 'clear' mode in bulk category modal with confirmation and API call
- Improve CSRF token usage and error handling during bulk update requests
- Remove deprecated handleClearAll function and integrate logic into handleApply
- Reset modal state properly including input fields and radio button modes
- Update modal JS file version reference in products list template

myproject/products/templates/products/products_list.html

@@ -486,5 +486,5 @@
 {% block extra_js %}
 {% load static %}
 <script src="{% static 'products/js/batch-selection.js' %}?v=1.2"></script>
-<script src="{% static 'products/js/bulk-category-modal.js' %}?v=1.4"></script>
+<script src="{% static 'products/js/bulk-category-modal.js' %}?v=1.6"></script>
 {% endblock %}