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.

config/__init__.py

@@ -182,7 +182,7 @@ def load_snowflake_config(config_path: Optional[Path] = None) -> SnowflakeConfig
     # Parse timeout settings
     timeout_data = data.get("timeouts", {})
     timeouts = TimeoutConfig(
-        connection_timeout=timeout_data.get("connection_timeout", 30),
+        connection_timeout=timeout_data.get("connection_timeout", 600),
         query_timeout=timeout_data.get("query_timeout", 300),
         login_timeout=timeout_data.get("login_timeout", 120),
     )