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/utils/course-completion.ts

@@ -5,7 +5,7 @@ import {
 } from '@cio/db/queries/course/course';
 import { setMemberCertificateEarned, setMemberCertificationEmailSent } from '@cio/db/queries/course/people';
 import { getProfileById } from '@cio/db/queries/auth';
-import { buildEmailFromName } from '@cio/email';
+import { buildEmailFromName, buildEmailBranding } from '@cio/email';
 import { enqueueTransactionalEmail } from '@api/services/jobs';
 
 export function calcCourseProgressPercent(params: {
@@ -81,7 +81,12 @@ export function scheduleCertificationCompletionWork(params: {
           courseName: courseRow.title,
           studentName: profile?.fullname || studentEmail,
           certificateUrl,
-          customMessage: courseRow.certificate?.emailMessage ?? null
+          customMessage: courseRow.certificate?.emailMessage ?? null,
+          branding: buildEmailBranding({
+            name: courseRow.orgName,
+            avatarUrl: courseRow.orgAvatarUrl,
+            theme: courseRow.orgTheme
+          })
         },
         from: buildEmailFromName(`${courseRow.orgName} (via ClassroomIO.com)`),
         idempotencyKey: `course-completion:${groupMemberId}`