fix(migration): ALTER TABLE to add new columns on existing supplementary tables

create_all() only creates missing tables; it won't modify tables that already
exist from an older schema version. Add _apply_schema_alterations() which runs
idempotent ADD COLUMN IF NOT EXISTS statements after every migration so
supplementary tables (like ofsted_inspections) gain new columns without
dropping their existing data.

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

backend/migration.py

@@ -404,6 +404,35 @@ def migrate_data(df: pd.DataFrame, geocode: bool = False, geocode_cache: dict =
         print("\nMigration complete!")
 
 
+def _apply_schema_alterations():
+    """
+    Add new columns to existing tables using ALTER TABLE … ADD COLUMN IF NOT EXISTS.
+    Safe to run on every migration — no-ops if the column already exists.
+    Add entries here whenever models.py gains new columns on an existing table.
+    """
+    alterations = [
+        # v4: Ofsted Report Card columns
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS framework VARCHAR(20)",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_safeguarding_met BOOLEAN",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_inclusion INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_curriculum_teaching INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_achievement INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_attendance_behaviour INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_personal_development INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_leadership_governance INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_early_years INTEGER",
+        "ALTER TABLE ofsted_inspections ADD COLUMN IF NOT EXISTS rc_sixth_form INTEGER",
+    ]
+    from sqlalchemy import text as sa_text
+    with engine.connect() as conn:
+        for stmt in alterations:
+            try:
+                conn.execute(sa_text(stmt))
+            except Exception as e:
+                print(f"  Warning: alteration skipped ({e})")
+        conn.commit()
+
+
 def run_full_migration(geocode: bool = False) -> bool:
     """
     Run a complete migration: drop all tables and reimport from CSV.
@@ -443,6 +472,13 @@ def run_full_migration(geocode: bool = False) -> bool:
     print("Creating all tables...")
     Base.metadata.create_all(bind=engine)
 
+    # ALTER existing supplementary tables to add any new columns.
+    # create_all() only creates missing tables; it won't add columns to tables
+    # that already exist from an older schema version.  These statements are
+    # idempotent (IF NOT EXISTS) so they're safe to run on every migration.
+    print("Applying column additions to supplementary tables...")
+    _apply_schema_alterations()
+
     print("\nLoading CSV data...")
     df = load_csv_data(settings.data_dir)