fix: eurostat JSON-stat parsing + staging model corrections

Eurostat JSON-stat format (4-7 dimension sparse dict with 583K values)
causes DuckDB OOM — pre-process in extractor to flat records.
Also fix dim_cities unused CTE bug and playtomic venue lat/lon path.

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

transform/sqlmesh_padelnomics/models/foundation/dim_cities.sql

@@ -15,7 +15,8 @@ eurostat_cities AS (
     city_code,
     country_code,
     population,
-    ref_year
+    ref_year,
+    LOWER(REPLACE(city_code, country_code, ''))  AS city_slug_raw
   FROM staging.stg_population
   QUALIFY ROW_NUMBER() OVER (PARTITION BY city_code ORDER BY ref_year DESC) = 1
 ),
@@ -30,16 +31,6 @@ venue_counts AS (
   FROM foundation.dim_venues
   WHERE city IS NOT NULL AND city != ''
   GROUP BY country_code, city
-),
--- Eurostat city label mapping to canonical city names
--- (Eurostat uses codes like DE001C → Berlin; we keep both)
-eurostat_labels AS (
-  SELECT DISTINCT
-    city_code,
-    country_code,
-    -- Derive a slug-friendly city name from the code as fallback
-    LOWER(REPLACE(city_code, country_code, ''))  AS city_slug_raw
-  FROM eurostat_cities
 )
 SELECT
   ec.city_code,