fix(transform): use community repository for h3 extension install

SQLMesh's extensions config supports dict form with 'repository' key,
which runs INSTALL h3 FROM community + LOAD h3 automatically at connect
time. No manual one-time install needed per machine.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

transform/sqlmesh_padelnomics/config.yaml

@@ -6,7 +6,8 @@ gateways:
         local: "{{ env_var('DUCKDB_PATH', 'data/lakehouse.duckdb') }}"
       extensions:
         - spatial
-        - h3
+        - name: h3
+          repository: community
 
 default_gateway: duckdb