chore: remove the Ofsted Parent View feature end to end

Removes the 'What Parents Say' section and all supporting elements:

Frontend:
- Drop the OfstedParentView type, the parent_view field, the survey
  section and the 'X% would recommend' callouts in the primary and
  secondary detail views, the Parents nav item, and the parent-view CSS.

Backend:
- Remove the FactParentView model, its loading in data_loader, and
  parent_view from the school-details API response.
- Bump SCHEMA_VERSION to 6 and add an idempotent drop step
  (DROP TABLE IF EXISTS marts.fact_parent_view) to the CLI migration;
  add scripts/sql/drop_fact_parent_view.sql to apply directly to the
  dbt-owned marts DBs on staging and prod.

Pipeline:
- Delete the stg_parent_view + fact_parent_view dbt models and their
  source/schema entries, the tap-uk-parent-view Meltano extractor, and
  the monthly Parent View DAG; drop it from the Dockerfile and the
  staging bootstrap docs.

The rest of dbt (which builds every mart the app reads) is untouched.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

backend/migration.py

@@ -433,6 +433,25 @@ def _apply_schema_alterations():
         conn.commit()
 
 
+def _apply_schema_drops():
+    """
+    Drop tables retired from the schema. Idempotent (DROP … IF EXISTS), so it's
+    safe to run on every migration. Add entries here when a model is removed.
+    """
+    drops = [
+        # v6: Ofsted Parent View feature removed
+        "DROP TABLE IF EXISTS marts.fact_parent_view CASCADE",
+    ]
+    from sqlalchemy import text as sa_text
+    with engine.connect() as conn:
+        for stmt in drops:
+            try:
+                conn.execute(sa_text(stmt))
+            except Exception as e:
+                print(f"  Warning: drop skipped ({e})")
+        conn.commit()
+
+
 def run_full_migration(geocode: bool = False) -> bool:
     """
     Run a complete migration: drop all tables and reimport from CSV.
@@ -479,6 +498,9 @@ def run_full_migration(geocode: bool = False) -> bool:
     print("Applying column additions to supplementary tables...")
     _apply_schema_alterations()
 
+    print("Dropping retired tables...")
+    _apply_schema_drops()
+
     print("\nLoading CSV data...")
     df = load_csv_data(settings.data_dir)