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.

packages/jobs/src/queues/names.ts

@@ -33,6 +33,11 @@ export const JOB_NAMES = {
   emails: {
     send: 'send'
   },
+  notifications: {
+    notifyCourseExercise: 'notify-course-exercise',
+    sessionReminderScan: 'session-reminder-scan',
+    notifyCourseSessionUpdate: 'notify-course-session-update'
+  },
   webhooks: {
     deliver: 'deliver'
   },