feat: copilot controller (#6272)

fix CLOUD-27

packages/backend/server/schema.prisma

@@ -97,7 +97,6 @@ model Workspace {
   permissions     WorkspaceUserPermission[]
   pagePermissions WorkspacePageUserPermission[]
   features        WorkspaceFeatures[]
-  aiSessions      AiSession[]
 
   @@map("workspaces")
 }
@@ -323,8 +322,6 @@ model Snapshot {
   // but the created time of last seen update that has been merged into snapshot.
   updatedAt   DateTime @map("updated_at") @db.Timestamptz(6)
 
-  aiSessions AiSession[]
-
   @@id([id, workspaceId])
   @@map("snapshots")
 }
@@ -485,11 +482,9 @@ model AiSession {
   promptName  String   @map("prompt_name") @db.VarChar(32)
   createdAt   DateTime @default(now()) @map("created_at") @db.Timestamptz(6)
 
-  user      User               @relation(fields: [userId], references: [id], onDelete: Cascade)
-  workspace Workspace          @relation(fields: [workspaceId], references: [id], onDelete: Cascade)
-  doc       Snapshot           @relation(fields: [docId, workspaceId], references: [id, workspaceId], onDelete: Cascade)
-  prompt    AiPrompt           @relation(fields: [promptName], references: [name], onDelete: Cascade)
-  messages  AiSessionMessage[]
+  user     User               @relation(fields: [userId], references: [id], onDelete: Cascade)
+  prompt   AiPrompt           @relation(fields: [promptName], references: [name], onDelete: Cascade)
+  messages AiSessionMessage[]
 
   @@map("ai_sessions_metadata")
 }