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/pages/settings.svelte

@@ -158,7 +158,8 @@
         grading: $settings.grading,
         lessonDownload: $settings.lessonDownload,
         allowNewStudent: $settings.allowNewStudents ?? false,
-        isContentGroupingEnabled: $settings.isContentGroupingEnabled
+        isContentGroupingEnabled: $settings.isContentGroupingEnabled,
+        progressionMode: $settings.progressionMode
       } as NonNullable<Course['metadata']>;
 
       const updatedCourse = {
@@ -222,6 +223,7 @@
         isPublished: !!course.isPublished,
         allowNewStudents: !!course.metadata?.allowNewStudent,
         isContentGroupingEnabled: course.metadata?.isContentGroupingEnabled ?? true,
+        progressionMode: course.metadata?.progressionMode ?? 'free',
         callout: normalizeCallout(course.callout)
       });
     });
@@ -522,6 +524,35 @@
 
   <Field.Separator />
 
+  <Field.Set>
+    <Field.Legend>{$t('course.navItem.settings.progression_mode_title')}</Field.Legend>
+    <Field.Description>{$t('course.navItem.settings.progression_mode_description')}</Field.Description>
+    <Field.Field>
+      <RadioGroup.Root
+        value={$settings.progressionMode}
+        onValueChange={(value) => {
+          if (value === 'free' || value === 'sequential') {
+            $settings.progressionMode = value;
+            hasUnsavedChanges = true;
+          }
+        }}
+      >
+        <div class="flex flex-col gap-3">
+          <div class="flex items-center gap-2">
+            <RadioGroup.Item value="free" id="progression-free" />
+            <Label for="progression-free">{$t('course.navItem.settings.progression_mode_free')}</Label>
+          </div>
+          <div class="flex items-center gap-2">
+            <RadioGroup.Item value="sequential" id="progression-sequential" />
+            <Label for="progression-sequential">{$t('course.navItem.settings.progression_mode_sequential')}</Label>
+          </div>
+        </div>
+      </RadioGroup.Root>
+    </Field.Field>
+  </Field.Set>
+
+  <Field.Separator />
+
   <Field.Set>
     <Field.Legend>{$t('course.navItem.settings.lesson_download')}</Field.Legend>
     <Field.Description>{$t('course.navItem.settings.available')}</Field.Description>
@@ -737,6 +768,7 @@
         checked={$settings.isPublished}
         onCheckedChange={(checked) => {
           $settings.isPublished = checked;
+          if (checked) $settings.allowNewStudents = true;
           hasUnsavedChanges = true;
         }}
       />