feat(discovery): migration 000017 — nullable bucket_id; model uses *uuid.UUID

backend/internal/domain/discovery/model.go

@@ -27,7 +27,7 @@ type Bucket struct {
 // vorjahr_unbestaetigt|abgesagt).
 type DiscoveredMarket struct {
 	ID               uuid.UUID  `json:"id"`
-	BucketID         uuid.UUID  `json:"bucket_id"`
+	BucketID         *uuid.UUID `json:"bucket_id"`
 	MarktName        string     `json:"markt_name"`
 	Stadt            string     `json:"stadt"`
 	Bundesland       string     `json:"bundesland"`

backend/internal/domain/discovery/service.go

@@ -205,7 +205,7 @@ func (s *Service) processBucketResponse(ctx context.Context, b Bucket, resp Pass
 		}
 
 		dm := DiscoveredMarket{
-			BucketID:        b.ID,
+			BucketID:        &b.ID,
 			MarktName:       m.MarktName,
 			Stadt:           m.Stadt,
 			Bundesland:      m.Bundesland,

backend/migrations/000017_discovered_markets_bucket_nullable.down.sql

@@ -0,0 +1,8 @@
+DO $$
+BEGIN
+  IF EXISTS (SELECT 1 FROM discovered_markets WHERE bucket_id IS NULL) THEN
+    RAISE EXCEPTION 'Cannot revert: % rows have NULL bucket_id (crawler-produced). Resolve manually before rolling back.',
+      (SELECT COUNT(*) FROM discovered_markets WHERE bucket_id IS NULL);
+  END IF;
+END $$;
+ALTER TABLE discovered_markets ALTER COLUMN bucket_id SET NOT NULL;

backend/migrations/000017_discovered_markets_bucket_nullable.up.sql

@@ -0,0 +1 @@
+ALTER TABLE discovered_markets ALTER COLUMN bucket_id DROP NOT NULL;