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/backend/src/db/migrations/0034_blocked_dates.sql

@@ -0,0 +1,21 @@
+-- Phase 4b: Instructor blocked dates, store closures, and substitute instructor on sessions
+
+ALTER TABLE "lesson_session"
+  ADD COLUMN "substitute_instructor_id" uuid REFERENCES "instructor"("id");
+
+CREATE TABLE "instructor_blocked_date" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  "instructor_id" uuid NOT NULL REFERENCES "instructor"("id"),
+  "start_date" date NOT NULL,
+  "end_date" date NOT NULL,
+  "reason" varchar(255),
+  "created_at" timestamptz NOT NULL DEFAULT now()
+);
+
+CREATE TABLE "store_closure" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  "name" varchar(255) NOT NULL,
+  "start_date" date NOT NULL,
+  "end_date" date NOT NULL,
+  "created_at" timestamptz NOT NULL DEFAULT now()
+);

packages/backend/src/db/migrations/meta/_journal.json

@@ -239,6 +239,13 @@
       "when": 1774930000000,
       "tag": "0033_lesson_plans",
       "breakpoints": true
+    },
+    {
+      "idx": 34,
+      "version": "7",
+      "when": 1774940000000,
+      "tag": "0034_blocked_dates",
+      "breakpoints": true
     }
   ]
 }

packages/backend/src/db/schema/lessons.ts

@@ -115,11 +115,31 @@ export const lessonSessions = pgTable('lesson_session', {
   nextLessonGoals: text('next_lesson_goals'),
   topicsCovered: text('topics_covered').array(),
   makeupForSessionId: uuid('makeup_for_session_id'),
+  substituteInstructorId: uuid('substitute_instructor_id').references(() => instructors.id),
   notesCompletedAt: timestamp('notes_completed_at', { withTimezone: true }),
   createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
   updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
 })
 
+export const instructorBlockedDates = pgTable('instructor_blocked_date', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  instructorId: uuid('instructor_id')
+    .notNull()
+    .references(() => instructors.id),
+  startDate: date('start_date').notNull(),
+  endDate: date('end_date').notNull(),
+  reason: varchar('reason', { length: 255 }),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+})
+
+export const storeClosures = pgTable('store_closure', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  name: varchar('name', { length: 255 }).notNull(),
+  startDate: date('start_date').notNull(),
+  endDate: date('end_date').notNull(),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+})
+
 export const gradingScales = pgTable('grading_scale', {
   id: uuid('id').primaryKey().defaultRandom(),
   name: varchar('name', { length: 255 }).notNull(),
@@ -210,6 +230,10 @@ export type Enrollment = typeof enrollments.$inferSelect
 export type EnrollmentInsert = typeof enrollments.$inferInsert
 export type LessonSession = typeof lessonSessions.$inferSelect
 export type LessonSessionInsert = typeof lessonSessions.$inferInsert
+export type InstructorBlockedDate = typeof instructorBlockedDates.$inferSelect
+export type InstructorBlockedDateInsert = typeof instructorBlockedDates.$inferInsert
+export type StoreClosure = typeof storeClosures.$inferSelect
+export type StoreClosureInsert = typeof storeClosures.$inferInsert
 export type GradingScale = typeof gradingScales.$inferSelect
 export type GradingScaleInsert = typeof gradingScales.$inferInsert
 export type GradingScaleLevel = typeof gradingScaleLevels.$inferSelect