feat(transform): H3 catchment index for Marktpotenzial-Score v3

Add H3 res-4 regional catchment metrics (~15-18km radius, cell + 6
neighbours) to both the addressable market (25pts) and supply gap
(30pts) components of location_opportunity_profile.

Changes:
- config.yaml: add h3 to DuckDB extensions (requires one-time
  INSTALL h3 FROM community on each machine)
- dim_locations: add h3_cell_res4 column via h3_latlng_to_cell()
- location_opportunity_profile: add hex_stats + catchment CTEs;
  update score formula to use catchment_population and
  catchment_padel_courts; expose catchment_population,
  catchment_padel_courts, catchment_venues_per_100k as output cols

Motivation: local population underestimates functional market for
mid-size cities (e.g. Oldenburg ~170K misses surrounding Gemeinden).
H3 k_ring(1) captures the realistic driving-distance catchment
(~462km²) consistently across both score components.

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

transform/sqlmesh_padelnomics/config.yaml

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