feat: add show_in_legal to admin content page editor

- Add "Show in Legal" checkbox to content page editor UI
- Update API schemas (ContentPageCreate, ContentPageUpdate, ContentPageResponse)
- Add show_in_legal parameter to service methods (create_page, update_page, etc.)
- Fix ContentPageNotFoundException to pass identifier correctly
- Fix UnauthorizedContentPageAccessException to use correct AuthorizationException API
- Add comprehensive unit tests for ContentPageService (35 tests)
- Add content page fixtures for testing
- Update CMS documentation with navigation categories diagram

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

static/admin/js/content-page-edit.js

@@ -27,6 +27,7 @@ function contentPageEditor(pageId) {
             is_published: false,
             show_in_header: false,
             show_in_footer: true,
+            show_in_legal: false,
             display_order: 0,
             vendor_id: null
         },
@@ -89,6 +90,7 @@ function contentPageEditor(pageId) {
                     is_published: page.is_published || false,
                     show_in_header: page.show_in_header || false,
                     show_in_footer: page.show_in_footer !== undefined ? page.show_in_footer : true,
+                    show_in_legal: page.show_in_legal || false,
                     display_order: page.display_order || 0,
                     vendor_id: page.vendor_id
                 };
@@ -125,6 +127,7 @@ function contentPageEditor(pageId) {
                     is_published: this.form.is_published,
                     show_in_header: this.form.show_in_header,
                     show_in_footer: this.form.show_in_footer,
+                    show_in_legal: this.form.show_in_legal,
                     display_order: this.form.display_order,
                     vendor_id: this.form.vendor_id
                 };