fix: migration compatible for postgres (#12659)

fix AI-162

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

- **Chores**
  - Improved database migration scripts to prevent errors by ensuring changes are only applied if relevant tables exist. No visible changes to user features or functionality.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/backend/server/migrations/20250429113337_workspace_file_blob_id/migration.sql

@@ -1,2 +1,9 @@
+DO $$
+    BEGIN
+        IF EXISTS (SELECT 1 FROM pg_tables WHERE tablename = 'ai_workspace_files') THEN
             -- AlterTable
-ALTER TABLE "ai_workspace_files" ADD COLUMN     "blob_id" VARCHAR NOT NULL DEFAULT '';
+            ALTER TABLE "ai_workspace_files"
+                ADD COLUMN "blob_id" VARCHAR NOT NULL DEFAULT '';
+        END IF;
+    END
+$$;

packages/backend/server/migrations/20250521083048_fix_workspace_embedding_chunk_primary_key/migration.sql

@@ -5,6 +5,10 @@
   - The primary key for the `ai_workspace_file_embeddings` table will be changed. If it partially fails, the table could be left without primary key constraint.
 
 */
+DO $$
+    BEGIN
+        IF EXISTS (SELECT 1 FROM pg_tables WHERE tablename = 'ai_workspace_embeddings') AND
+           EXISTS (SELECT 1 FROM pg_tables WHERE tablename = 'ai_workspace_file_embeddings') THEN
             -- DropIndex
             DROP INDEX "ai_workspace_embeddings_workspace_id_doc_id_chunk_key";
 
@@ -12,9 +16,14 @@ DROP INDEX "ai_workspace_embeddings_workspace_id_doc_id_chunk_key";
             DROP INDEX "ai_workspace_file_embeddings_workspace_id_file_id_chunk_key";
 
             -- AlterTable
-ALTER TABLE "ai_workspace_embeddings" DROP CONSTRAINT "ai_workspace_embeddings_pkey",
+            ALTER TABLE "ai_workspace_embeddings"
+                DROP CONSTRAINT "ai_workspace_embeddings_pkey",
                 ADD CONSTRAINT "ai_workspace_embeddings_pkey" PRIMARY KEY ("workspace_id", "doc_id", "chunk");
 
             -- AlterTable
-ALTER TABLE "ai_workspace_file_embeddings" DROP CONSTRAINT "ai_workspace_file_embeddings_pkey",
+            ALTER TABLE "ai_workspace_file_embeddings"
+                DROP CONSTRAINT "ai_workspace_file_embeddings_pkey",
                 ADD CONSTRAINT "ai_workspace_file_embeddings_pkey" PRIMARY KEY ("workspace_id", "file_id", "chunk");
+        END IF;
+    END
+$$;