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/docs/content/docs/course.mdx

@@ -5,7 +5,7 @@ description: Overview of courses in ClassroomIO — lifecycle, settings, admin a
 
 import { Callout } from 'fumadocs-ui/components/callout';
 
-A **course** in ClassroomIO is a container for lessons, exercises, people, and settings. Students enroll into a course to access its content in the LMS. This page summarizes how courses work for admins. For step-by-step setup, start with [Creating Your First Course](/docs/how-to-guides/create-first-course).
+A **course** in ClassroomIO is a container for lessons, exercises, people, and settings. Students enroll into a course to access its content in the LMS. This page summarizes how courses work for admins. For step-by-step setup, start with [Creating Your First Course](/docs/create-first-course).
 
 ## Course lifecycle
 
@@ -15,7 +15,7 @@ A **course** in ClassroomIO is a container for lessons, exercises, people, and s
 | **Published** | Live on your academy; visible in Explore and on the public landing page |
 | **Deleted** | Soft-deleted; no longer appears anywhere in the app |
 
-Publishing makes a course discoverable. Combine publish state with **Allow New Students**, price, and invites to control who can actually join. See [How Course Enrollment Works](/docs/how-to-guides/course-enrollment).
+Publishing makes a course discoverable. Combine publish state with **Allow New Students**, price, and invites to control who can actually join. See [How Course Enrollment Works](/docs/course-enrollment).
 
 ## Key settings
 
@@ -27,7 +27,7 @@ Publishing makes a course discoverable. Combine publish state with **Allow New S
 | **Course type** | Course **Settings** | Changes nav, compliance, and public access behavior |
 
 <Callout type="info" title="Course type changes more than a label">
-  Self-paced, Live class, Compliance, and Public types change what admins and students see in the app. See [Course Types](/docs/how-to-guides/course-types) for when to use each.
+  Self-paced, Live class, Compliance, and Public types change what admins and students see in the app. See [Course Types](/docs/course-types) for when to use each.
 </Callout>
 
 ## Admin areas inside a course
@@ -47,7 +47,7 @@ When you open a course from the **Courses** list, the sidebar gives you:
 
 The **People** tab lists everyone in the course group. Members appear when they enroll or when you add them from **Add people**. Email-only invites show as **Pending** until the student signs in.
 
-Enrollment paths (public, invite link, admin assignment, paid) are documented in [How Course Enrollment Works](/docs/how-to-guides/course-enrollment). For sending invites, see [How to Invite Students](/docs/how-to-guides/invite-students).
+Enrollment paths (public, invite link, admin assignment, paid) are documented in [How Course Enrollment Works](/docs/course-enrollment). For sending invites, see [How to Invite Students](/docs/invite-students).
 
 ## What students see
 
@@ -55,10 +55,10 @@ After enrolling, students open the course from **Home** or **My Learning** in th
 
 ## Related guides
 
-- [Creating Your First Course](/docs/how-to-guides/create-first-course)
-- [Course Types](/docs/how-to-guides/course-types)
-- [How Course Enrollment Works](/docs/how-to-guides/course-enrollment)
-- [How to Invite Students](/docs/how-to-guides/invite-students)
-- [Create a Course Landing Page](/docs/how-to-guides/course-landingpage)
+- [Creating Your First Course](/docs/create-first-course)
+- [Course Types](/docs/course-types)
+- [How Course Enrollment Works](/docs/course-enrollment)
+- [How to Invite Students](/docs/invite-students)
+- [Create a Course Landing Page](/docs/course-landingpage)
 - [Student Dashboard](/docs/student-dashboard)