fix+test: check hash ref count on copy-on-write (a duplicated beeing updated)

src/infrastructure/repositories/pg/file_blob_write_repository.rs

@@ -606,15 +606,14 @@ impl FileWritePort for FileBlobWriteRepository {
     async fn delete_file_permanently(&self, file_id: &str) -> Result<(), DomainError> {
         // Read blob_hash before deletion so we can clean up disk after the
         // PG trigger has decremented the ref_count.
-        let blob_hash: Option<String> = sqlx::query_scalar(
-            "SELECT blob_hash FROM storage.files WHERE id = $1::uuid",
-        )
-        .bind(file_id)
-        .fetch_optional(self.pool.as_ref())
-        .await
-        .map_err(|e| {
-            DomainError::internal_error("FileBlobWrite", format!("fetch blob_hash: {e}"))
-        })?;
+        let blob_hash: Option<String> =
+            sqlx::query_scalar("SELECT blob_hash FROM storage.files WHERE id = $1::uuid")
+                .bind(file_id)
+                .fetch_optional(self.pool.as_ref())
+                .await
+                .map_err(|e| {
+                    DomainError::internal_error("FileBlobWrite", format!("fetch blob_hash: {e}"))
+                })?;
 
         // DELETE fires trg_files_decrement_blob_ref → storage.blobs.ref_count--
         self.delete_file(file_id).await?;