feat: improve LMS course discovery and enrollment UX

- Add paginated recommended courses to LMS dashboard (top 3, list
    view)
    and explore page (12 per page); exclude courses blocking new
    students
  - Polish course preview modal: remove padding, render requirements as
    HTML, round banner image, secondary close button
  - Redirect to course start page after successful enrollment instead of
    /lms;
    keep spinner active until navigation completes
  - Auto-enable "allow new students" when a course is published
  - Move Explore after My Learning in LMS sidebar nav
  - Move Certificates after Content in course sidebar
  - Add hiddenColumns prop to CourseListRow; show "Learn more" button
    instead of actions menu in LMS explore context

apps/dashboard/src/lib/features/course/components/sidebar/course-sidebar-navigation.svelte

@@ -89,6 +89,19 @@
         isLesson: true,
         icon: getNavIcon(NAV_IDS.LESSONS)
       },
+      {
+        id: NAV_IDS.CERTIFICATES,
+        title: $t('course.navItems.nav_certificates'),
+        url: getNavItemRoute(id, 'certificates'),
+        isActive: (path || page.url.pathname) === getNavItemRoute(id, 'certificates'),
+        show() {
+          if (isStudent && $isFreePlan) {
+            return false;
+          }
+          return true;
+        },
+        icon: getNavIcon(NAV_IDS.CERTIFICATES)
+      },
       {
         id: NAV_IDS.ANALYTICS,
         title: $t('course.navItems.nav_analytics'),
@@ -144,19 +157,6 @@
         },
         icon: getNavIcon(NAV_IDS.COMPLIANCE)
       },
-      {
-        id: NAV_IDS.CERTIFICATES,
-        title: $t('course.navItems.nav_certificates'),
-        url: getNavItemRoute(id, 'certificates'),
-        isActive: (path || page.url.pathname) === getNavItemRoute(id, 'certificates'),
-        show() {
-          if (isStudent && $isFreePlan) {
-            return false;
-          }
-          return true;
-        },
-        icon: getNavIcon(NAV_IDS.CERTIFICATES)
-      },
       {
         id: NAV_IDS.LANDING_PAGE,
         title: $t('course.navItems.nav_landing_page'),