Add Phase 8: lesson plan templates with deep-copy instantiation

- New tables: lesson_plan_template, lesson_plan_template_section, lesson_plan_template_item
- skill_level enum: beginner, intermediate, advanced, all_levels
- Templates are reusable curriculum definitions independent of any member/enrollment
- POST /lesson-plan-templates/:id/create-plan deep-copies the template into a member plan
- Instantiation uses template name as default plan title, accepts custom title override
- Instantiation deactivates any existing active plan on the enrollment (one-active rule)
- Plan items are independent copies — renaming the template does not affect existing plans
- 11 new integration tests

packages/shared/src/schemas/index.ts

@@ -126,6 +126,10 @@ export {
   StoreClosureCreateSchema,
   GradeCreateSchema,
   SessionPlanItemsSchema,
+  SkillLevel,
+  LessonPlanTemplateCreateSchema,
+  LessonPlanTemplateUpdateSchema,
+  TemplateInstantiateSchema,
 } from './lessons.schema.js'
 export type {
   InstructorCreateInput,
@@ -149,4 +153,7 @@ export type {
   StoreClosureCreateInput,
   GradeCreateInput,
   SessionPlanItemsInput,
+  LessonPlanTemplateCreateInput,
+  LessonPlanTemplateUpdateInput,
+  TemplateInstantiateInput,
 } from './lessons.schema.js'