fix: increase network timeout and batch size for GP lookup queries (Task 3.2)

Dry run test revealed GP lookup queries timing out at 30s (connection_timeout
in snowflake.toml). Increased to 600s. Also increased batch_size from 500 to
5000 — query time is ~40s regardless of batch size (CTE compilation overhead),
so larger batches reduce total time from ~50min to ~6min for 36K patients.

Dry run results: 91.8% GP match rate, 49.3% drug-indication match rate,
42,072 modified UPIDs, 1,846 pathway nodes across 6 date filters.

data_processing/diagnosis_lookup.py

@@ -1568,7 +1568,7 @@ AllIndicationCodes AS (
 def get_patient_indication_groups(
     patient_pseudonyms: list[str],
     connector: Optional[SnowflakeConnector] = None,
-    batch_size: int = 500,
+    batch_size: int = 5000,
     earliest_hcd_date: Optional[str] = None,
 ) -> "pd.DataFrame":
     """