feat: add action_dropdown macro with loading state support

- Create action_dropdown macro in dropdowns.html supporting:
  - Loading/disabled state via loading_var parameter
  - Custom loading label
  - Icon support
  - Primary/secondary variants
- Update code quality dashboard to use new macro
- Add Dropdowns section to components page with examples:
  - Basic dropdown
  - Action dropdown with loading state
  - Context menu (3-dot)
  - Variant showcase (primary, secondary, ghost)

Architecture validation now passes with 0 errors and 0 warnings.

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/admin/js/components.js

@@ -27,6 +27,7 @@ function adminComponents() {
             { id: 'tabs', name: 'Tabs', icon: 'view-boards' },
             { id: 'forms', name: 'Forms', icon: 'clipboard-list' },
             { id: 'buttons', name: 'Buttons', icon: 'cursor-click' },
+            { id: 'dropdowns', name: 'Dropdowns', icon: 'chevron-down' },
             { id: 'cards', name: 'Cards', icon: 'collection' },
             { id: 'badges', name: 'Badges', icon: 'tag' },
             { id: 'tables', name: 'Tables', icon: 'table' },