⚡ (analytics) Improve analytics graph accuracy

packages/prisma/postgresql/schema.prisma

@@ -255,6 +255,7 @@ model Answer {
   createdAt   DateTime @default(now()) @updatedAt
   resultId    String
   blockId     String
+  itemId      String?
   groupId     String
   variableId  String?
   content     String
@@ -262,7 +263,7 @@ model Answer {
   result      Result   @relation(fields: [resultId], references: [id], onDelete: Cascade)
 
   @@unique([resultId, blockId, groupId])
-  @@index([groupId])
+  @@index([blockId, itemId])
   @@index([storageUsed])
 }