Feature/table parser column roles (#13710)

### What problem does this PR solve?

The table file parser (CSV/Excel) currently treats all columns
identically — every column is both vectorized (embedded in chunk text)
and stored as filterable metadata. There's no way for users to control
which columns should be searchable by semantic meaning versus which
should only be filterable attributes.

For example, when ingesting a news articles CSV with columns like title,
content, country, category, source, etc., the embedding includes
metadata fields like country: Brazil and source: Reuters in the chunk
text, which dilutes the semantic quality of the embedding without adding
retrieval value.

The RDBMS connector (MySQL/PostgreSQL) already supports content_columns
/ metadata_columns, but this capability was missing for file-based table
ingestion.

This PR adds column-level control (vectorize / metadata / both) for the
table file parser, following RAGFlow's existing patterns.

Backward compatible: Datasets without table_column_roles or with
table_column_mode: auto behave exactly as before (all columns = both).

### Type of change

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

test/unit_test/api/utils/test_doc_validation.py

@@ -18,14 +18,15 @@
 
 from unittest.mock import Mock
 from api.utils.validation_utils import (
-    validate_immutable_fields,
+    ParserConfig,
+    UpdateDocumentReq,
+    validate_chunk_method,
     validate_document_name,
-    validate_chunk_method
+    validate_immutable_fields,
 )
 from api.constants import FILE_NAME_LEN_LIMIT
 from api.db import FileType
 from common.constants import RetCode
-from api.utils.validation_utils import UpdateDocumentReq
 
 
 def test_validate_immutable_fields_no_changes():
@@ -299,4 +300,15 @@ def test_validate_chunk_method_other_extensions_still_valid():
     
     error_msg, error_code = validate_chunk_method(doc)
     assert error_msg is None
-    assert error_code is None
+    assert error_code is None
+
+
+def test_parser_config_normalizes_legacy_vectorize_table_column_role():
+    p = ParserConfig(
+        table_column_roles={"title": "vectorize", "country": "metadata", "x": "both"},
+    )
+    assert p.table_column_roles == {
+        "title": "indexing",
+        "country": "metadata",
+        "x": "both",
+    }