Add Phase 4b: instructor blocked dates, store closures, and substitute instructors

- New tables: instructor_blocked_date, store_closure (migration 0034)
- substitute_instructor_id column added to lesson_session
- Session generation skips blocked instructor dates and store closure periods
- Substitute assignment validates sub is not blocked and has no conflicting slot
- Routes: POST/GET/DELETE /instructors/:id/blocked-dates, POST/GET/DELETE /store-closures
- 15 new integration tests covering blocked dates, store closures, and sub validation

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

@@ -104,9 +104,28 @@ export type LessonSessionNotesInput = z.infer<typeof LessonSessionNotesSchema>
 export const LessonSessionUpdateSchema = z.object({
   actualStartTime: opt(z.string().regex(/^\d{2}:\d{2}$/, 'Must be HH:MM format')),
   actualEndTime: opt(z.string().regex(/^\d{2}:\d{2}$/, 'Must be HH:MM format')),
+  substituteInstructorId: opt(z.string().uuid()),
 })
 export type LessonSessionUpdateInput = z.infer<typeof LessonSessionUpdateSchema>
 
+// --- Instructor Blocked Date schemas ---
+
+export const InstructorBlockedDateCreateSchema = z.object({
+  startDate: z.string().min(1),
+  endDate: z.string().min(1),
+  reason: opt(z.string().max(255)),
+})
+export type InstructorBlockedDateCreateInput = z.infer<typeof InstructorBlockedDateCreateSchema>
+
+// --- Store Closure schemas ---
+
+export const StoreClosureCreateSchema = z.object({
+  name: z.string().min(1).max(255),
+  startDate: z.string().min(1),
+  endDate: z.string().min(1),
+})
+export type StoreClosureCreateInput = z.infer<typeof StoreClosureCreateSchema>
+
 // --- Grading Scale schemas ---
 
 export const GradingScaleLevelInput = z.object({