fix(list): read ofsted grade from fact_ofsted_inspection directly, fix dim_school schema lookup

dim_school.sql was checking for int_ofsted_latest in target.schema (wrong schema)
due to the custom generate_schema_name macro using literal schema names. The
model lives in 'intermediate', so ofsted_grade/date/framework were always NULL
in dim_school, causing all list cards to show 'Not yet inspected'.

Fix 1: data_loader.py joins marts.fact_ofsted_inspection with DISTINCT ON to
get latest inspection per school — no pipeline re-run needed.

Fix 2: dim_school.sql uses schema='intermediate' so future dbt runs correctly
denormalise the Ofsted summary into dim_school.

backend/data_loader.py

@@ -130,9 +130,9 @@ _MAIN_QUERY = text("""
         s.total_pupils         AS gias_total_pupils,
         s.headteacher_name,
         s.website,
-        s.ofsted_grade,
-        s.ofsted_date,
-        s.ofsted_framework,
+        foi.ofsted_grade,
+        foi.ofsted_date,
+        foi.ofsted_framework,
         l.local_authority_name AS local_authority,
         l.local_authority_code,
         l.address_line1        AS address1,
@@ -201,6 +201,15 @@ _MAIN_QUERY = text("""
     FROM marts.dim_school s
     JOIN marts.dim_location l ON s.urn = l.urn
     LEFT JOIN marts.fact_performance p ON s.urn = p.urn
+    LEFT JOIN (
+        SELECT DISTINCT ON (urn)
+            urn,
+            overall_effectiveness AS ofsted_grade,
+            inspection_date       AS ofsted_date,
+            framework             AS ofsted_framework
+        FROM marts.fact_ofsted_inspection
+        ORDER BY urn, inspection_date DESC NULLS LAST
+    ) foi ON s.urn = foi.urn
     ORDER BY s.school_name, p.year
 """)