fix(gateway): address SonarQube PR-mode findings on F2/F3 code

- data_sink.py: _IDENTIFIER_RE uses \w+/re.ASCII instead of the
  equivalent-but-verbose [A-Za-z0-9_]+ character class (verified same
  match behavior). NOSONAR on update_write_status's 'async with no
  await inside' - deliberate, per the ponytail comment already in the
  method body (uniform async interface across DataSink, no async pg driver).
- test_grpc_server.py: move make_request() out of the pytest.raises
  block so exactly one call can raise the expected exception.
- sonar-project.properties: exclude ingestor/proto/ (generated grpc
  code) from analysis - its ReadTag/etc. names are dictated by
  grpcio-tools, not a style choice, and renaming them breaks the wire.

ingestor/io/data_sink.py

@@ -6,7 +6,7 @@ import ingestor.metrics as metrics
 
 # 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_]+')
+_IDENTIFIER_RE = re.compile(r'\w+', re.ASCII)
 
 
 class DataSink:
@@ -42,7 +42,7 @@ class DataSink:
                 },
             )
 
-    async def update_write_status(self, cmd: dict, result) -> None:
+    async def update_write_status(self, cmd: dict, result) -> None:  # NOSONAR
         """UPDATE the per-model prediction row's write_status (C3), by timestamp+model_id.
 
         schema/table_name are per-model SQL identifiers, not values — they can't be