Add lessons Phase 6: lesson plans with curriculum tracking

Structured lesson plans with nested sections and items per enrollment.
Deep create in one request, one-active-per-enrollment constraint,
auto-set startedDate/masteredDate on status transitions, progress %
calculation (skipped items excluded). 8 new tests (84 total).

packages/backend/src/db/migrations/0033_lesson_plans.sql

@@ -0,0 +1,43 @@
+-- Phase 6: Lesson plans — structured curriculum per enrollment
+
+CREATE TYPE "lesson_plan_item_status" AS ENUM ('not_started', 'in_progress', 'mastered', 'skipped');
+
+CREATE TABLE "member_lesson_plan" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  "member_id" uuid NOT NULL REFERENCES "member"("id"),
+  "enrollment_id" uuid NOT NULL REFERENCES "enrollment"("id"),
+  "created_by" uuid REFERENCES "user"("id"),
+  "title" varchar(255) NOT NULL,
+  "description" text,
+  "is_active" boolean NOT NULL DEFAULT true,
+  "started_date" date,
+  "completed_date" date,
+  "created_at" timestamptz NOT NULL DEFAULT now(),
+  "updated_at" timestamptz NOT NULL DEFAULT now()
+);
+
+CREATE TABLE "lesson_plan_section" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  "lesson_plan_id" uuid NOT NULL REFERENCES "member_lesson_plan"("id"),
+  "title" varchar(255) NOT NULL,
+  "description" text,
+  "sort_order" integer NOT NULL,
+  "created_at" timestamptz NOT NULL DEFAULT now()
+);
+
+CREATE TABLE "lesson_plan_item" (
+  "id" uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+  "section_id" uuid NOT NULL REFERENCES "lesson_plan_section"("id"),
+  "title" varchar(255) NOT NULL,
+  "description" text,
+  "status" lesson_plan_item_status NOT NULL DEFAULT 'not_started',
+  "grading_scale_id" uuid REFERENCES "grading_scale"("id"),
+  "current_grade_value" varchar(50),
+  "target_grade_value" varchar(50),
+  "started_date" date,
+  "mastered_date" date,
+  "notes" text,
+  "sort_order" integer NOT NULL,
+  "created_at" timestamptz NOT NULL DEFAULT now(),
+  "updated_at" timestamptz NOT NULL DEFAULT now()
+);