Add lessons domain Phase 1: instructor and lesson type entities

Foundation tables for the lessons module with full CRUD, pagination,
search, and sorting. Includes migration, Drizzle schema, Zod validation,
services, routes, and 23 integration tests.

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

@@ -0,0 +1,47 @@
+import {
+  pgTable,
+  uuid,
+  varchar,
+  text,
+  timestamp,
+  boolean,
+  integer,
+  pgEnum,
+} from 'drizzle-orm/pg-core'
+import { users } from './users.js'
+
+// --- Enums ---
+
+export const lessonFormatEnum = pgEnum('lesson_format', ['private', 'group'])
+
+// --- Tables ---
+
+export const instructors = pgTable('instructor', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  userId: uuid('user_id').references(() => users.id),
+  displayName: varchar('display_name', { length: 255 }).notNull(),
+  bio: text('bio'),
+  instruments: text('instruments').array(),
+  isActive: boolean('is_active').notNull().default(true),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+})
+
+export const lessonTypes = pgTable('lesson_type', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  name: varchar('name', { length: 255 }).notNull(),
+  instrument: varchar('instrument', { length: 100 }),
+  durationMinutes: integer('duration_minutes').notNull(),
+  lessonFormat: lessonFormatEnum('lesson_format').notNull().default('private'),
+  baseRateMonthly: varchar('base_rate_monthly', { length: 20 }),
+  isActive: boolean('is_active').notNull().default(true),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+})
+
+// --- Type exports ---
+
+export type Instructor = typeof instructors.$inferSelect
+export type InstructorInsert = typeof instructors.$inferInsert
+export type LessonType = typeof lessonTypes.$inferSelect
+export type LessonTypeInsert = typeof lessonTypes.$inferInsert