feat(codes): code NOT NULL voor PBI/Story + Task.code + product_id denorm

- Pbi.code en Story.code worden NOT NULL (tot dusver optional)
- Task krijgt code String + product_id String denorm + @@unique([product_id, code])
- Product krijgt back-relation tasks Task[]
- Migratie backfillt bestaande NULL-rijen via PL/pgSQL:
  PBI-N (per product), ST-N (3-digit padded met GREATEST om
  truncatie van LPAD bij 4-digit nummers te voorkomen),
  T-N voor alle tasks
- Codes zijn stabiele identifiers (Jira-stijl flat-per-product),
  zodat re-parenting de code niet muteert

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

prisma/migrations/20260504055000_codes_required_and_task_code/migration.sql

@@ -0,0 +1,75 @@
+-- Codes verplicht maken voor PBI/Story en code-kolom + product_id denorm
+-- toevoegen aan Task. Bestaande NULL-rijen worden gevuld via PL/pgSQL backfill.
+
+-- 1) Tasks: product_id denorm (eerst nullable, backfill, dan NOT NULL + FK)
+ALTER TABLE "tasks" ADD COLUMN "product_id" TEXT;
+UPDATE "tasks" t SET "product_id" = s."product_id" FROM "stories" s WHERE s."id" = t."story_id";
+ALTER TABLE "tasks" ALTER COLUMN "product_id" SET NOT NULL;
+ALTER TABLE "tasks" ADD CONSTRAINT "tasks_product_id_fkey" FOREIGN KEY ("product_id") REFERENCES "products"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- 2) Tasks: code (eerst nullable t.b.v. backfill)
+ALTER TABLE "tasks" ADD COLUMN "code" VARCHAR(30);
+
+-- 3) Backfill PBI codes (alleen NULL-rijen, per product, op created_at)
+DO $$
+DECLARE rec RECORD;
+DECLARE n INT;
+BEGIN
+  FOR rec IN SELECT DISTINCT product_id FROM "pbis" WHERE code IS NULL LOOP
+    SELECT COALESCE(MAX(CAST(SUBSTRING(code FROM 'PBI-(\d+)$') AS INTEGER)), 0)
+      INTO n
+      FROM "pbis"
+      WHERE product_id = rec.product_id AND code ~ '^PBI-\d+$';
+    UPDATE "pbis" SET code = 'PBI-' || (n + sub.row_num)
+      FROM (
+        SELECT id, ROW_NUMBER() OVER (ORDER BY created_at, id) AS row_num
+        FROM "pbis"
+        WHERE product_id = rec.product_id AND code IS NULL
+      ) sub
+      WHERE "pbis".id = sub.id;
+  END LOOP;
+END $$;
+
+-- 4) Backfill Story codes (TO_CHAR met FM-format: padding tot minimaal 3 chars zonder truncatie)
+DO $$
+DECLARE rec RECORD;
+DECLARE n INT;
+BEGIN
+  FOR rec IN SELECT DISTINCT product_id FROM "stories" WHERE code IS NULL LOOP
+    SELECT COALESCE(MAX(CAST(SUBSTRING(code FROM 'ST-(\d+)$') AS INTEGER)), 0)
+      INTO n
+      FROM "stories"
+      WHERE product_id = rec.product_id AND code ~ '^ST-\d+$';
+    UPDATE "stories" SET code = 'ST-' || LPAD((n + sub.row_num)::TEXT, GREATEST(3, LENGTH((n + sub.row_num)::TEXT)), '0')
+      FROM (
+        SELECT id, ROW_NUMBER() OVER (ORDER BY created_at, id) AS row_num
+        FROM "stories"
+        WHERE product_id = rec.product_id AND code IS NULL
+      ) sub
+      WHERE "stories".id = sub.id;
+  END LOOP;
+END $$;
+
+-- 5) Backfill Task codes (alle rijen — kolom net toegevoegd)
+DO $$
+DECLARE rec RECORD;
+BEGIN
+  FOR rec IN SELECT DISTINCT product_id FROM "tasks" WHERE code IS NULL LOOP
+    UPDATE "tasks" SET code = 'T-' || sub.row_num
+      FROM (
+        SELECT id, ROW_NUMBER() OVER (ORDER BY created_at, id) AS row_num
+        FROM "tasks"
+        WHERE product_id = rec.product_id AND code IS NULL
+      ) sub
+      WHERE "tasks".id = sub.id;
+  END LOOP;
+END $$;
+
+-- 6) NOT NULL constraints
+ALTER TABLE "pbis" ALTER COLUMN "code" SET NOT NULL;
+ALTER TABLE "stories" ALTER COLUMN "code" SET NOT NULL;
+ALTER TABLE "tasks" ALTER COLUMN "code" SET NOT NULL;
+
+-- 7) Unique + lookup index op Task
+CREATE UNIQUE INDEX "tasks_product_id_code_key" ON "tasks"("product_id", "code");
+CREATE INDEX "tasks_product_id_idx" ON "tasks"("product_id");