fix: include catalog.hpp directly in pyconnection.cpp

pyconnection.cpp uses Catalog::GetCatalog/GetSystemCatalog but relied on
a transitive include of duckdb/catalog/catalog.hpp via
function/table_function.hpp -> execution/physical_operator_states.hpp.
duckdb main removed that include chain (~2026-07-10), so PR and nightly
CI - which build against duckdb main via the duckdb-sha override - fail
to compile with "incomplete type 'duckdb::Catalog'". Include the header
directly.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: NickCrews

src/pyconnection.cpp

@@ -1,5 +1,6 @@
 #include "duckdb_python/pyconnection/pyconnection.hpp"
 
+#include "duckdb/catalog/catalog.hpp"
 #include "duckdb/common/arrow/arrow.hpp"
 #include "duckdb/common/types.hpp"
 #include "duckdb/common/types/vector.hpp"