feat: live class sessions, CE workflow, and docs (#683)

Adds live-class session scheduling on lessons (join link, date/time,
timezone) with automatic 24h and 1h reminder emails plus a calendar
invite (.ics), a time-change notification with an updated invite, a
teacher-authored welcome email and session invite on enrollment, and a
"Notify students" quiz nudge.

LMS gets an upcoming live-sessions card and Join buttons, plus a
reusable live-session card component (3 states) in @cio/ui with a
Storybook story. The sidebar content tree now reflects sequential
progression locking like the content list, and the course-completion
confetti regression is fixed.

Org-based emails no longer reference ClassroomIO by name. Docs add
live-class, welcome-email, and course-progression guides, expand the
certificates guide (design, signatures, corrected labels), move
plan-required callouts to the top, flatten how-to-guides to the docs
root with redirects, and add screenshots. Includes an add-docs-image
skill.

apps/api/src/routes/course/course.ts

@@ -35,6 +35,7 @@ import { courseAiTutorRouter } from '@api/routes/course/ai-tutor';
 import { authMiddleware } from '@api/middlewares/auth';
 import { authOrAutomationKeyMiddleware } from '@api/middlewares/auth-or-automation-key';
 import { cloneCourse } from '@api/services/course/clone';
+import { sanitizeHtml } from '@cio/core/utils/sanitize-html';
 import { complianceRouter } from '@api/routes/course/compliance';
 import { contentRouter } from '@api/routes/course/content';
 import { courseMemberMiddleware } from '@api/middlewares/course-member';
@@ -329,6 +330,13 @@ export const courseRouter = new Hono()
         const validatedData = c.req.valid('json');
         const { tagIds, ...courseData } = validatedData;
 
+        if (courseData.metadata?.welcomeEmailMessage) {
+          courseData.metadata = {
+            ...courseData.metadata,
+            welcomeEmailMessage: sanitizeHtml(courseData.metadata.welcomeEmailMessage)
+          };
+        }
+
         const result = await updateCourse(courseId, courseData);
 
         if (tagIds !== undefined) {

apps/api/src/routes/course/exercise.ts

@@ -29,8 +29,14 @@ import {
   initVideoRecordingUpload
 } from '@api/services/exercise/video-recording';
 
+import {
+  getNotifyCourseExerciseStatusService,
+  notifyCourseExerciseService
+} from '@api/services/course/notify-exercise';
+
 import { Hono } from '@api/utils/hono';
 import { authMiddleware } from '@api/middlewares/auth';
+import { courseTeamMemberMiddleware } from '@api/middlewares/course-team-member';
 import { authOrAutomationKeyMiddleware } from '@api/middlewares/auth-or-automation-key';
 import { courseMemberMiddleware } from '@api/middlewares/course-member';
 import { courseMemberOrAutomationKeyMiddleware } from '@api/middlewares/course-member-or-automation-key';
@@ -82,6 +88,28 @@ export const exerciseRouter = new Hono()
       return handleError(c, error, 'Failed to fetch exercise submissions overview');
     }
   })
+  .post('/:exerciseId/notify', authMiddleware, courseTeamMemberMiddleware, async (c) => {
+    try {
+      const courseId = c.req.param('courseId')!;
+      const exerciseId = c.req.param('exerciseId')!;
+
+      const result = await notifyCourseExerciseService(courseId, exerciseId);
+      return c.json({ success: true, data: result }, 202);
+    } catch (error) {
+      return handleError(c, error, 'Failed to notify students');
+    }
+  })
+  .get('/:exerciseId/notify/:jobId', authMiddleware, courseTeamMemberMiddleware, async (c) => {
+    try {
+      const jobId = c.req.param('jobId')!;
+      const pollCount = Number.parseInt(c.req.query('pollCount') ?? '0', 10) || 0;
+
+      const envelope = await getNotifyCourseExerciseStatusService(jobId, pollCount);
+      return c.json({ success: true, data: envelope }, 200);
+    } catch (error) {
+      return handleError(c, error, 'Failed to fetch notification status');
+    }
+  })
   .get(
     '/:exerciseId',
     authOrAutomationKeyMiddleware,

apps/api/src/routes/course/lesson.ts

@@ -38,6 +38,8 @@ import { Hono } from '@api/utils/hono';
 import { ZLessonDownloadContent } from '@cio/utils/validation/course';
 import { authMiddleware } from '@api/middlewares/auth';
 import { courseMemberMiddleware } from '@api/middlewares/course-member';
+import { courseTeamMemberMiddleware } from '@api/middlewares/course-team-member';
+import { notifyCourseSessionUpdateService } from '@api/services/course/notify-session';
 import { generateLessonPdf } from '@api/utils/lesson';
 import { getGroupMemberIdByCourseAndProfile } from '@cio/db/queries/group';
 import { handleError } from '@api/utils/errors';
@@ -121,6 +123,23 @@ export const lessonRouter = new Hono()
       }
     }
   )
+  .post(
+    '/:lessonId/notify-session-update',
+    authMiddleware,
+    courseTeamMemberMiddleware,
+    zValidator('param', ZLessonGetParam),
+    async (c) => {
+      try {
+        const courseId = c.req.param('courseId')!;
+        const { lessonId } = c.req.valid('param');
+
+        const result = await notifyCourseSessionUpdateService(courseId, lessonId);
+        return c.json({ success: true, data: result }, 202);
+      } catch (error) {
+        return handleError(c, error, 'Failed to notify session update');
+      }
+    }
+  )
   .delete('/:lessonId', authMiddleware, courseMemberMiddleware, zValidator('param', ZLessonGetParam), async (c) => {
     try {
       const { lessonId } = c.req.valid('param');