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/organization/invite.ts

@@ -32,6 +32,7 @@ import { getDashboardBaseUrl } from '@cio/core/config/dashboard-url';
 import { parseCourseIdsFromInviteMetadata, parseProgramIdsFromInviteMetadata } from '@api/utils/org';
 import { markUserAndProfileEmailVerified } from '@cio/db/queries/auth/profile';
 import { enqueueTransactionalEmail } from '@api/services/jobs';
+import { buildEmailBranding } from '@cio/email';
 import { ensureComplianceEnrollmentRecordsForProfiles } from '../course/compliance';
 
 type OrganizationInviteStatus = 'ACTIVE' | 'EXPIRED' | 'REVOKED' | 'ACCEPTED';
@@ -60,8 +61,11 @@ function normalizeEmails(emails: string[]): string[] {
   return [...new Set(emails.map((email) => email.toLowerCase().trim()).filter(Boolean))];
 }
 
-function buildInviteLink(token: string): string {
-  return `${getDashboardBaseUrl()}/invite/${encodeURIComponent(token)}`;
+function buildInviteLink(
+  token: string,
+  org?: { siteName?: string | null; customDomain?: string | null; isCustomDomainVerified?: boolean | null }
+): string {
+  return `${getDashboardBaseUrl(org)}/invite/${encodeURIComponent(token)}`;
 }
 
 function getRoleLabel(roleId: number): string {
@@ -245,7 +249,7 @@ export async function inviteTeamMembers(orgId: string, emails: string[], roleId:
         }
       });
 
-      const inviteLink = buildInviteLink(token);
+      const inviteLink = buildInviteLink(token, organization);
 
       try {
         await enqueueTransactionalEmail('inviteTeacher', {
@@ -256,7 +260,8 @@ export async function inviteTeamMembers(orgId: string, emails: string[], roleId:
             orgSiteName: organization.siteName,
             roleName,
             expiresAt: getExpiryLabel(expiresAt),
-            inviteLink
+            inviteLink,
+            branding: buildEmailBranding(organization)
           },
           idempotencyKey: `org-invite-teacher:${invite.id}`
         });