Fix: table parser metadata (#15127)

### What problem does this PR solve?

This PR improves the table upload flow for CSV/Excel files by allowing
table column role configuration at upload time.

Previously, users had to:
1. Upload and parse a table file.
2. Open parser settings and manually set table column roles.
3. Re-parse the file for the roles to take effect.

This was inefficient and required an unnecessary second parse.

With this change:
1. When the knowledge base uses table parsing, the upload dialog
extracts CSV/Excel headers client-side.
2. Users can choose Auto mode or Manual mode.
3. In Manual mode, users can assign per-column roles before upload.
4. The selected parser config is sent with the upload request and
applied server-side during document creation.

Result: configured table column roles are applied from the first parse.

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

Co-authored-by: Ahmad Intisar <ahmadintisar@Ahmads-MacBook-M4-Pro.local>

api/apps/restful_apis/document_api.py

@@ -585,9 +585,25 @@ async def _upload_local_documents(kb, tenant_id):
             logging.error(msg)
             return get_error_data_result(message=msg, code=RetCode.ARGUMENT_ERROR)
 
+    # Parse optional parser_config overrides from form data
+    parser_config_override = None
+    raw_parser_config = form.get("parser_config")
+    if raw_parser_config:
+        try:
+            parsed = json.loads(raw_parser_config)
+            if isinstance(parsed, dict):
+                # Only allow known table column config keys to prevent arbitrary overrides
+                allowed_keys = {"table_column_mode", "table_column_roles"}
+                parser_config_override = {k: v for k, v in parsed.items() if k in allowed_keys}
+                if not parser_config_override:
+                    parser_config_override = None
+        except (json.JSONDecodeError, TypeError):
+            parser_config_override = None
+
     err, files = await thread_pool_exec(
         FileService.upload_document, kb, file_objs, tenant_id,
-        parent_path=form.get("parent_path")
+        parent_path=form.get("parent_path"),
+        parser_config_override=parser_config_override,
     )
     if err:
         msg = "\n".join(err)