fix(gateway): tighten SQL identifier validation to fullmatch (reject trailing newline)

ingestor/io/data_sink.py

@@ -4,7 +4,9 @@ from sqlalchemy import text
 
 import ingestor.metrics as metrics
 
-_IDENTIFIER_RE = re.compile(r'^[A-Za-z0-9_]+$')
+# fullmatch (no ^/$ anchors) so a trailing newline can't slip through — `$` would
+# match before a trailing '\n', which is not what we want for a SQL identifier.
+_IDENTIFIER_RE = re.compile(r'[A-Za-z0-9_]+')
 
 
 class DataSink:
@@ -63,6 +65,6 @@ class DataSink:
 
     @staticmethod
     def _validate_identifier(name: str) -> str:
-        if not _IDENTIFIER_RE.match(name):
+        if not isinstance(name, str) or not _IDENTIFIER_RE.fullmatch(name):
             raise ValueError(f'invalid SQL identifier: {name!r}')
         return name