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/services/program/goal.ts

@@ -1,6 +1,7 @@
 import { AppError, ErrorCodes } from '@api/utils/errors';
 import { enqueueTransactionalEmail } from '@api/services/jobs';
 import { getDashboardBaseUrl } from '@cio/core/config/dashboard-url';
+import { buildEmailBranding } from '@cio/email';
 import {
   countAssignmentsByStatus,
   createProgramGoal,
@@ -425,7 +426,12 @@ export async function runProgramGoalReminderScan(): Promise<{
           daysUntilDue,
           completedCount: row.assignment.completedCount ?? 0,
           requiredCount: row.assignment.requiredCount ?? 0,
-          loginUrl: `${loginUrl}/lms/programs/${row.programId}`
+          loginUrl: `${loginUrl}/lms/programs/${row.programId}`,
+          branding: buildEmailBranding({
+            name: row.organizationName,
+            avatarUrl: row.organizationAvatarUrl,
+            theme: row.organizationTheme
+          })
         },
         idempotencyKey: `program-goal-reminder:${row.assignment.id}:${daysUntilDue}:${dayKey}`
       });