fix(server): embedding chunks primary key (#12416)

fix AI-131

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **Refactor**
  - Updated database schema to consolidate unique constraints into composite primary keys for embedding-related data, improving consistency.
  - Changed the relation in the Snapshot model to allow multiple embeddings.
  - Improved filtering logic for documents and snapshots based on embedding existence.
  - Reformatted SQL queries and schema attributes for improved readability; no changes to functionality.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/src/models/copilot-context.ts

@@ -210,9 +210,12 @@ export class CopilotContextModel extends BaseModel {
     );
     await this.db.$executeRaw`
       INSERT INTO "ai_workspace_embeddings"
-      ("workspace_id", "doc_id", "chunk", "content", "embedding", "updated_at") VALUES ${values}
-      ON CONFLICT (workspace_id, doc_id, chunk) DO UPDATE SET
-      embedding = EXCLUDED.embedding, updated_at = excluded.updated_at;
+        ("workspace_id", "doc_id", "chunk", "content", "embedding", "updated_at")
+      VALUES ${values}
+      ON CONFLICT (workspace_id, doc_id, chunk)
+      DO UPDATE SET
+        embedding = EXCLUDED.embedding,
+        updated_at = excluded.updated_at;
     `;
   }
 

packages/backend/server/src/models/copilot-workspace.ts

@@ -47,7 +47,7 @@ export class CopilotWorkspaceConfigModel extends BaseModel {
         where: {
           workspaceId,
           embedding: {
-            is: null,
+            none: {},
           },
         },
         select: { id: true },