feat(billing): enforce free-plan student cap across the app (#733)

* feat(billing): enforce free-plan student cap across the app

Free (BASIC) plan orgs were able to exceed the advertised 20-student
limit because the cap existed only as dashboard cosmetic copy with no
server-side enforcement.

Add a single source of truth (getStudentLimit / STUDENT_LIMITS) and a
central guard (assertStudentCapacityOrThrow) wired into every path that
creates a new student-role org member: self-enrolment, course-invite
acceptance, bulk audience import, and org-invite acceptance. The guard
throws UPGRADE_REQUIRED (403) and notifies org admins by email (throttled
to once per org per day) when the limit is hit.

Surface the limit in the UI: disable the audience import button and the
course new-student invite section with upgrade banners for admins, and
show a "contact your administrator" message on the public enrol page for
students (who cannot upgrade). Expose a studentLimitReached flag from the
public course endpoint so the enrol button can be disabled proactively.

Add a one-time (manual, non-cron) db script,
db:notify-students-over-limit, to email admins of orgs already over the
limit at rollout.

* feat(billing): guard remaining student-creating paths against the cap

The initial cap enforcement missed several service entry points that also
create a new student-role org member. Add the capacity guard to:

- autoEnrollStudent (public org self-join on a tenant site)
- cohort enrollment (bulk group enrollment and single member accept)
- ensureProgramCourseAccess (program/cohort-granted course access)

For the cohort and program paths, only genuinely new members are counted
(existing org members are skipped) so re-enrolling current students is
never falsely blocked. The core path enforces via the shared limit check;
it throws UPGRADE_REQUIRED without the admin email since the queue lives
in the api layer.

* fix(billing): don't show cap block to existing org members on enroll page

The public course-by-slug endpoint is unauthenticated, so the enroll
page's studentLimitReached flag is org-wide and can't tell whether the
current viewer is already an org member. An existing student of a full
BASIC org would see Join disabled even though the backend correctly lets
existing members enroll without consuming a new seat.

Only pre-block anonymous visitors (would-be new joiners). Logged-in users
are governed by the membership-aware backend, which allows existing
members and returns UPGRADE_REQUIRED (surfaced via the enroll onError
mapping) for genuinely new students.

* feat(billing): deliver org plan-limits via /account with an extensible registry

Replace the ad-hoc, per-surface audience fetches (each calling getOrgAudience
just to read a count) with a single, future-proof delivery of org usage +
limits on the /account payload, gated to admin/tutor members (students never
receive limit data; a plain COUNT, no student rows).

Model it generically so future org limits (courses, etc.) drop in without
reshaping the payload or re-plumbing the frontend:
- New packages/utils plan-limits registry: PLAN_LIMIT_RESOURCES, PLAN_LIMITS
  (reuses STUDENT_LIMITS), getPlanLimit, and a JSON-safe ResourceUsage /
  OrgUsageLimits shape with isResourceLimitReached / resourceLimitRemaining.
- getAccountData attaches a per-org `limits` map for admin/tutor orgs.
- Store selectors currentOrgLimits / studentUsage / isStudentLimitReached;
  sidebars, upgrade card, People pages, and invite modals read these instead
  of fetching audience rows.

Bring cohort surfaces to parity with course: cohort People page banner and
cohort sidebar People upgrade icon, matching the course equivalents.

Also: close the upgrade modal that opened over the invite modal (drop the
`add` param via openUpgradeModalOver), redesign the sidebar upgrade card
(progress toward the student limit), add a Progress `variant`, and document
the no-complex-expressions-in-object-literals rule in AGENTS.md.

* refactor(billing): address PR review on the limits work

- Dedupe new student profile IDs before the cohort seat check so duplicate
  batch entries can't overcount against the cap (Greptile P1).
- Drive the org-sidebar upgrade indicator from a dynamic nav-item `upgrade`
  flag (audience config declares `upgradeResource: 'students'`; groups set it
  from a `limitsReached` map) instead of a hardcoded path check.
- Collapse the audience Import button into a single button with ternary
  `disabled`/`href`.
- Simplify the notify-students-over-limit upgrade link to app.classroomio.com.
- Drop the comment on the org `limits` field.
- Add .greptile/rules.md documenting the manual one-time db/src/scripts
  convention (operator-controlled reruns) so idempotency isn't reflagged.

* fix(billing): name the org in the enroll capacity message

Change the enroll-page student-limit message from "This course has reached
its student capacity" to "{orgName} has reached its student capacity", since
the cap is org-wide, not course-specific. Pass orgName from the loaded org on
the page and from the currentOrg store in the enroll onError snackbar.

* style(billing): use PremiumIcon for the Authentication upgrade indicator

Replace the RocketIcon on paid settings sub-items (e.g. Authentication) with
the PremiumIcon used on the Audience item, right-aligned (ml-auto) to match.

packages/db/src/queries/organization/organization.ts

@@ -567,6 +567,58 @@ export const getOrganizationTeam = async (orgId: string) => {
   }));
 };
 
+/**
+ * Counts active organization members with the student role. Used to enforce per-plan student caps.
+ */
+export async function countActiveStudents(orgId: string): Promise<number> {
+  try {
+    const [row] = await db
+      .select({ count: count(schema.organizationmember.id) })
+      .from(schema.organizationmember)
+      .where(
+        and(eq(schema.organizationmember.organizationId, orgId), eq(schema.organizationmember.roleId, ROLE.STUDENT))
+      );
+
+    return Number(row?.count ?? 0);
+  } catch (error) {
+    console.error('countActiveStudents error:', error);
+    throw new Error('Failed to count active students');
+  }
+}
+
+/**
+ * Gets verified admin emails for an organization. Used to notify admins about plan-limit events.
+ */
+export async function getOrganizationAdminEmails(orgId: string): Promise<Array<{ email: string; fullname: string }>> {
+  try {
+    const result = await db
+      .select({
+        email: schema.organizationmember.email,
+        profileEmail: schema.profile.email,
+        fullname: schema.profile.fullname
+      })
+      .from(schema.organizationmember)
+      .leftJoin(schema.profile, eq(schema.organizationmember.profileId, schema.profile.id))
+      .where(
+        and(
+          eq(schema.organizationmember.organizationId, orgId),
+          eq(schema.organizationmember.roleId, ROLE.ADMIN),
+          eq(schema.organizationmember.verified, true)
+        )
+      );
+
+    return result
+      .map((member) => ({
+        email: member.profileEmail || member.email || '',
+        fullname: member.fullname || ''
+      }))
+      .filter((member) => member.email);
+  } catch (error) {
+    console.error('getOrganizationAdminEmails error:', error);
+    throw new Error('Failed to get organization admin emails');
+  }
+}
+
 /**
  * Gets organization audience (all organization members with student role).
  * Includes invited members without a profile (LEFT JOIN profile).

packages/db/src/queries/organization/types.ts

@@ -1,4 +1,5 @@
 import { TOrganization, TOrganizationPlan } from '@db/types';
+import type { OrgUsageLimits } from '@cio/utils/plans';
 
 export type OrganizationPlan = Pick<TOrganizationPlan, 'planName' | 'isActive' | 'provider' | 'subscriptionId'> & {
   customerId: string | null;
@@ -8,6 +9,7 @@ export type OrganizationWithMemberAndPlans = TOrganization & {
   memberId?: number;
   roleId?: number;
   plans: OrganizationPlan[];
+  limits?: OrgUsageLimits;
 };
 
 export type OrganizationWithPlans = TOrganization & {

packages/db/src/scripts/notify-students-over-limit.ts

@@ -0,0 +1,70 @@
+/**
+ * One-time (manual, not cron) backfill: email admins of every free-plan org
+ * that already exceeds the student limit, so they know new enrolments/invites
+ * are now blocked. Dry-run by default; pass --execute to actually send.
+ *
+ * Usage:
+ *   pnpm db:notify-students-over-limit             # dry run (default)
+ *   pnpm db:notify-students-over-limit -- --execute # send emails
+ */
+import 'dotenv/config';
+
+import { buildEmailBranding, sendEmail } from '@cio/email';
+import { PLAN, getStudentLimit, isOrgOnFreePlan } from '@cio/utils/plans';
+
+import {
+  countActiveStudents,
+  getOrganizationAdminEmails,
+  getOrganizations
+} from '../queries/organization/organization';
+
+async function main() {
+  const execute = process.argv.includes('--execute');
+  const orgs = await getOrganizations();
+  const limit = getStudentLimit(PLAN.BASIC);
+
+  let notified = 0;
+
+  for (const org of orgs) {
+    const isFree = isOrgOnFreePlan({ plans: org.plans, isSelfHosted: false, orgId: org.id });
+    if (!isFree) continue;
+
+    const studentCount = await countActiveStudents(org.id);
+    if (studentCount <= limit) continue;
+
+    const admins = await getOrganizationAdminEmails(org.id);
+    if (!admins.length) {
+      console.log(`Skipping ${org.name} (${org.id}): ${studentCount}/${limit} but no admin emails`);
+      continue;
+    }
+
+    console.log(
+      `${execute ? 'Notifying' : '[dry-run] Would notify'} ${org.name} (${org.id}): ${studentCount}/${limit} students → ${admins.length} admin(s)`
+    );
+
+    if (execute) {
+      const branding = buildEmailBranding({ name: org.name, avatarUrl: org.avatarUrl, theme: org.theme });
+      const upgradeUrl = `https://app.classroomio.com/org/${org.siteName ?? ''}?upgrade=true`;
+
+      await Promise.all(
+        admins.map((admin) =>
+          sendEmail('studentLimitReached', {
+            to: admin.email,
+            fields: { orgName: org.name, studentCount, studentLimit: limit, upgradeUrl, branding }
+          })
+        )
+      );
+
+      notified++;
+    }
+  }
+
+  console.log(execute ? `Done. Notified ${notified} org(s).` : 'Dry run complete — re-run with --execute to send.');
+}
+
+main()
+  .then(() => process.exit(0))
+  .catch((error) => {
+    console.error(error);
+    process.exit(1);
+  });