Fix encoding issue by enforcing UTF-8 content type for transformed document uploads (#387)

* fix: Update content type mapping in document transformation service to include charset for markdown

* pre commit

Author: avirajsingh7

backend/app/core/doctransform/service.py

@@ -89,11 +89,7 @@ def execute_job(
         convert_document(tmp_in, tmp_out, transformer_name)
 
         # Determine content type based on target format
-        content_type_map = {
-            "markdown": "text/markdown",
-            "text": "text/plain",
-            "html": "text/html",
-        }
+        content_type_map = {"markdown": "text/markdown; charset=utf-8"}
         content_type = content_type_map.get(target_format, "text/plain")
 
         # upload transformed file and create document record