fix: fix: asyncpg bouncer connection pool error

Prepared statement caching is disabled by setting
`statement_cache_size=0` in the `asyncpg` connection pool parameters.
This is necessary to prevent
`asyncpg.exceptions.InvalidSQLStatementNameError` when using
transaction-level connection poolers like Supabase Supavisor or
pgbouncer, which do not support prepared statements.

lightrag/kg/postgres_impl.py

@@ -161,6 +161,7 @@ class PostgreSQLDB:
                 "port": self.port,
                 "min_size": 1,
                 "max_size": self.max,
+                "statement_cache_size": 0,
             }
 
             # Add SSL configuration if provided