merge(worktree): interactive maps for market pages

Self-hosted Leaflet 1.9.4 maps across 4 placements: markets hub
country bubbles, country overview city bubbles, city venue dots, and
a standalone opportunity map. New /api blueprint with 4 JSON endpoints.
New city_venue_locations SQLMesh serving model. No CDN — GDPR-safe.

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

# Conflicts:
#	CHANGELOG.md

transform/sqlmesh_padelnomics/models/serving/city_venue_locations.sql

@@ -0,0 +1,26 @@
+-- Per-venue lat/lon for the city detail dot map.
+-- Joins dim_venues to dim_cities to attach country_slug and city_slug
+-- (needed by the /api/markets/<country>/<city>/venues.json endpoint).
+-- Only rows with valid coordinates are included.
+
+MODEL (
+  name serving.city_venue_locations,
+  kind FULL,
+  cron '@daily',
+  grain venue_id
+);
+
+SELECT
+  v.venue_id,
+  v.name,
+  v.lat,
+  v.lon,
+  v.court_count,
+  v.indoor_court_count,
+  v.outdoor_court_count,
+  v.city_slug,
+  c.country_slug
+FROM foundation.dim_venues v
+JOIN foundation.dim_cities c
+  ON v.country_code = c.country_code AND v.city_slug = c.city_slug
+WHERE v.lat IS NOT NULL AND v.lon IS NOT NULL

transform/sqlmesh_padelnomics/models/serving/pseo_city_costs_de.sql

@@ -26,6 +26,9 @@ SELECT
   c.country_code,
   c.country_name_en,
   c.country_slug,
+  -- City coordinates (for the city venue dot map)
+  c.lat,
+  c.lon,
   -- Market metrics
   c.population,
   c.padel_venue_count,