chore: relocate backend into apps/api ahead of monorepo merge

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/api/database/migrations/20270101000050-create-pages.js

@@ -0,0 +1,34 @@
+'use strict';
+
+module.exports = {
+  async up(queryInterface, Sequelize) {
+    await queryInterface.createTable('pages', {
+      id: {
+        type:          Sequelize.BIGINT,
+        autoIncrement: true,
+        primaryKey:    true,
+      },
+      type: {
+        type:      Sequelize.ENUM('landing_page', 'lesson_page', 'course_page'),
+        allowNull: false,
+      },
+      created_at: {
+        type:         Sequelize.DATE,
+        allowNull:    false,
+        defaultValue: Sequelize.literal('CURRENT_TIMESTAMP'),
+      },
+      updated_at: {
+        type:         Sequelize.DATE,
+        allowNull:    false,
+        defaultValue: Sequelize.literal('CURRENT_TIMESTAMP'),
+      },
+    });
+
+    await queryInterface.addIndex('pages', { fields: ['type'], name: 'idx_pages_type' });
+  },
+
+  async down(queryInterface) {
+    await queryInterface.dropTable('pages');
+    await queryInterface.sequelize.query('DROP TYPE IF EXISTS "enum_pages_type";');
+  },
+};