fix(lms): support direct R2 map uploads and preserve empty course groups

prisma/migrations/20260909060000_group_course_scope/migration.sql

@@ -0,0 +1,19 @@
+ALTER TABLE "student_groups" ADD COLUMN "course_id" UUID;
+CREATE INDEX "student_groups_course_id_idx" ON "student_groups"("course_id");
+ALTER TABLE "student_groups" ADD CONSTRAINT "student_groups_course_id_fkey"
+  FOREIGN KEY ("course_id") REFERENCES "courses"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+
+-- Preserve only unambiguous historical course associations. Empty groups without
+-- curriculum history cannot be attributed to an instructor safely.
+WITH candidates AS (
+  SELECT "group_id", "course_id" FROM "instructor_curriculum_settings" WHERE "group_id" IS NOT NULL
+  UNION
+  SELECT m."group_id", e."course_id"
+  FROM "student_group_members" m
+  JOIN "student_enrollments" e ON e."user_id" = m."user_id" AND e."status" = 'ACTIVE'
+), unique_courses AS (
+  SELECT "group_id", MIN("course_id"::text)::uuid AS "course_id"
+  FROM candidates GROUP BY "group_id" HAVING COUNT(DISTINCT "course_id") = 1
+)
+UPDATE "student_groups" g SET "course_id" = c."course_id"
+FROM unique_courses c WHERE g."id" = c."group_id";

prisma/schema.prisma

@@ -65,6 +65,8 @@ model StudentEnrollment {
 
 model StudentGroup {
   id               String               @id @default(uuid()) @db.Uuid
+  courseId         String?              @map("course_id") @db.Uuid
+  course           Course?              @relation(fields: [courseId], references: [id], onDelete: Restrict)
   organizationId   String?              @map("organization_id") @db.Uuid
   organizationName String               @map("organization_name")
   name             String
@@ -84,6 +86,7 @@ model StudentGroup {
   teamCustomModules TeamCustomModule[]
 
   @@unique([organizationName, name])
+  @@index([courseId])
   @@index([organizationId])
   @@index([organizationName])
   @@index([instructorPlatformId])
@@ -168,6 +171,7 @@ model Course {
   customModules   StudentCustomModule[]
   teamCustomModules TeamCustomModule[]
   submissionScores SubmissionScore[]
+  studentGroups    StudentGroup[]
   submissionTotalScores SubmissionTotalScore[]
 
   @@index([isActive])