refactor: align transform layer with template methodology

Three deviations from the quart_saas_boilerplate methodology corrected:

1. Fix dim_cities LIKE join (data quality bug)
   - Old: FROM eurostat_cities LEFT JOIN venue_counts LIKE '%country_code%'
     → cartesian product (2.6M rows vs ~5500 expected)
   - New: FROM venue_cities (dim_venues) as primary table, Eurostat for
     enrichment only. grain (country_code, city_slug).
   - Also fixes REGEXP_REPLACE to LOWER() before regex so uppercase city
     names aren't stripped to '-'

2. Rename fct_venue_capacity → dim_venue_capacity
   - Static venue attributes with no time key are a dimension, not a fact
   - No SQL logic changes; update fct_daily_availability reference

3. Add fct_availability_slot at event grain
   - New: grain (snapshot_date, tenant_id, resource_id, slot_start_time)
   - Recheck dedup logic moves here from fct_daily_availability
   - fct_daily_availability now reads fct_availability_slot (cleaner DAG)

Downstream fixes:
- city_market_profile, planner_defaults grain → (country_code, city_slug)
- pseo_city_costs_de, pseo_city_pricing add city_key composite natural key
  (country_slug || '-' || city_slug) to avoid URL collisions across countries
- planner_defaults join in pseo_city_costs_de uses both country_code + city_slug
- Templates updated: natural_key city_slug → city_key

Added transform/sqlmesh_padelnomics/CLAUDE.md documenting data modeling rules,
conformed dimension map, and source integration architecture.

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

transform/sqlmesh_padelnomics/models/foundation/fct_availability_slot.sql

@@ -0,0 +1,56 @@
+-- Slot-level availability fact: one row per deduplicated available slot.
+-- Event grain: (snapshot_date, tenant_id, resource_id, slot_start_time).
+--
+-- "Available" means the slot was NOT booked at capture time.
+-- Recheck-aware: for each (date, tenant, resource, start_time), prefer the
+-- latest recheck snapshot over the morning snapshot. If a slot was present
+-- in the morning but absent in the recheck, that means it was booked between
+-- snapshots — and it will simply not appear in this model (correct behaviour:
+-- unavailable slots are not in the available-slots fact).
+--
+-- is_peak: convenience flag for 17:00–21:00 slots (main evening rush).
+-- Downstream models (fct_daily_availability) use this to avoid re-computing
+-- the peak window condition on every aggregation.
+
+MODEL (
+  name foundation.fct_availability_slot,
+  kind FULL,
+  cron '@daily',
+  grain (snapshot_date, tenant_id, resource_id, slot_start_time)
+);
+
+WITH deduped AS (
+  SELECT
+    snapshot_date,
+    tenant_id,
+    resource_id,
+    slot_start_time,
+    price_amount,
+    price_currency,
+    snapshot_type,
+    captured_at_utc,
+    -- Prefer recheck over morning; within same snapshot_type prefer latest capture
+    ROW_NUMBER() OVER (
+      PARTITION BY snapshot_date, tenant_id, resource_id, slot_start_time
+      ORDER BY
+        CASE WHEN snapshot_type = 'recheck' THEN 1 ELSE 2 END,
+        captured_at_utc DESC
+    ) AS rn
+  FROM staging.stg_playtomic_availability
+  WHERE price_amount IS NOT NULL
+    AND price_amount > 0
+)
+SELECT
+  snapshot_date,
+  tenant_id,
+  resource_id,
+  slot_start_time,
+  price_amount,
+  price_currency,
+  snapshot_type,
+  captured_at_utc,
+  (   slot_start_time::TIME >= '17:00:00'
+  AND slot_start_time::TIME <  '21:00:00'
+  )                                              AS is_peak
+FROM deduped
+WHERE rn = 1