Add lessons Phase 3: enrollments with capacity and time conflict checks

Links members to schedule slots via enrollments. Enforces max_students
capacity on slots and prevents members from double-booking the same
day/time. Supports status transitions and filtering. 11 new tests
(51 total lessons tests).

packages/shared/src/schemas/index.ts

@@ -108,6 +108,10 @@ export {
   LessonTypeUpdateSchema,
   ScheduleSlotCreateSchema,
   ScheduleSlotUpdateSchema,
+  EnrollmentStatus,
+  EnrollmentCreateSchema,
+  EnrollmentUpdateSchema,
+  EnrollmentStatusUpdateSchema,
 } from './lessons.schema.js'
 export type {
   InstructorCreateInput,
@@ -116,4 +120,7 @@ export type {
   LessonTypeUpdateInput,
   ScheduleSlotCreateInput,
   ScheduleSlotUpdateInput,
+  EnrollmentCreateInput,
+  EnrollmentUpdateInput,
+  EnrollmentStatusUpdateInput,
 } from './lessons.schema.js'

packages/shared/src/schemas/lessons.schema.ts

@@ -51,3 +51,33 @@ export type ScheduleSlotCreateInput = z.infer<typeof ScheduleSlotCreateSchema>
 
 export const ScheduleSlotUpdateSchema = ScheduleSlotCreateSchema.partial()
 export type ScheduleSlotUpdateInput = z.infer<typeof ScheduleSlotUpdateSchema>
+
+// --- Enrollment schemas ---
+
+export const EnrollmentStatus = z.enum(['active', 'paused', 'cancelled', 'completed'])
+export type EnrollmentStatus = z.infer<typeof EnrollmentStatus>
+
+export const EnrollmentCreateSchema = z.object({
+  memberId: z.string().uuid(),
+  accountId: z.string().uuid(),
+  scheduleSlotId: z.string().uuid(),
+  instructorId: z.string().uuid(),
+  startDate: z.string().min(1),
+  endDate: opt(z.string()),
+  monthlyRate: z.coerce.number().min(0).optional(),
+  notes: opt(z.string()),
+})
+export type EnrollmentCreateInput = z.infer<typeof EnrollmentCreateSchema>
+
+export const EnrollmentUpdateSchema = EnrollmentCreateSchema.omit({
+  memberId: true,
+  accountId: true,
+  scheduleSlotId: true,
+  instructorId: true,
+}).partial()
+export type EnrollmentUpdateInput = z.infer<typeof EnrollmentUpdateSchema>
+
+export const EnrollmentStatusUpdateSchema = z.object({
+  status: EnrollmentStatus,
+})
+export type EnrollmentStatusUpdateInput = z.infer<typeof EnrollmentStatusUpdateSchema>