feat: migrate backend to marts schema, update EES tap for verified datasets

Pipeline:
- EES tap: split KS4 into performance + info streams, fix admissions filename
  (SchoolLevel keyword match), fix census filename (yearly suffix), remove
  phonics (no school-level data on EES), change endswith → in for matching
- stg_ees_ks4: rewrite to filter long-format data and extract Attainment 8,
  Progress 8, EBacc, English/Maths metrics; join KS4 info for context
- stg_ees_admissions: map real CSV columns (total_number_places_offered, etc.)
- stg_ees_census: update source reference, stub with TODO for data columns
- Remove stg_ees_phonics, fact_phonics (no school-level EES data)
- Add ees_ks4_performance + ees_ks4_info sources, remove ees_ks4 + ees_phonics
- Update int_ks4_with_lineage + fact_ks4_performance with new KS4 columns
- Annual EES DAG: remove stg_ees_phonics+ from selector

Backend:
- models.py: replace all models to point at marts.* tables with schema='marts'
  (DimSchool, DimLocation, KS2Performance, FactOfstedInspection, etc.)
- data_loader.py: rewrite load_school_data_as_dataframe() using raw SQL joining
  dim_school + dim_location + fact_ks2_performance; update get_supplementary_data()
- database.py: remove migration machinery, keep only connection setup
- app.py: remove check_and_migrate_if_needed, remove /api/admin/reimport-ks2
  endpoints (pipeline handles all imports)

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

backend/database.py

@@ -1,36 +1,30 @@
 """
 Database connection setup using SQLAlchemy.
+The schema is managed by dbt — the backend only reads from marts.* tables.
 """
 
-from datetime import datetime
-from typing import Optional
-
-from sqlalchemy import create_engine, inspect
-from sqlalchemy.orm import sessionmaker, declarative_base
 from contextlib import contextmanager
 
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker, declarative_base
+
 from .config import settings
 
-# Create engine
 engine = create_engine(
     settings.database_url,
     pool_size=10,
     max_overflow=20,
-    pool_pre_ping=True,  # Verify connections before use
-    echo=False,  # Set to True for SQL debugging
+    pool_pre_ping=True,
+    echo=False,
 )
 
-# Session factory
 SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
 
-# Base class for models
 Base = declarative_base()
 
 
 def get_db():
-    """
-    Dependency for FastAPI routes to get a database session.
-    """
+    """Dependency for FastAPI routes."""
     db = SessionLocal()
     try:
         yield db
@@ -40,10 +34,7 @@ def get_db():
 
 @contextmanager
 def get_db_session():
-    """
-    Context manager for database sessions.
-    Use in non-FastAPI contexts (scripts, etc).
-    """
+    """Context manager for non-FastAPI contexts."""
     db = SessionLocal()
     try:
         yield db
@@ -53,95 +44,3 @@ def get_db_session():
         raise
     finally:
         db.close()
-
-
-def init_db():
-    """
-    Initialize database - create all tables.
-    """
-    Base.metadata.create_all(bind=engine)
-
-
-def drop_db():
-    """
-    Drop all tables - use with caution!
-    """
-    Base.metadata.drop_all(bind=engine)
-
-
-def get_db_schema_version() -> Optional[int]:
-    """
-    Get the current schema version from the database.
-    Returns None if table doesn't exist or no version is set.
-    """
-    from .models import SchemaVersion  # Import here to avoid circular imports
-
-    # Check if schema_version table exists
-    inspector = inspect(engine)
-    if "schema_version" not in inspector.get_table_names():
-        return None
-
-    try:
-        with get_db_session() as db:
-            row = db.query(SchemaVersion).first()
-            return row.version if row else None
-    except Exception:
-        return None
-
-
-def set_db_schema_version(version: int):
-    """
-    Set/update the schema version in the database.
-    Creates the row if it doesn't exist.
-    """
-    from .models import SchemaVersion
-
-    with get_db_session() as db:
-        row = db.query(SchemaVersion).first()
-        if row:
-            row.version = version
-            row.migrated_at = datetime.utcnow()
-        else:
-            db.add(SchemaVersion(id=1, version=version, migrated_at=datetime.utcnow()))
-
-
-def check_and_migrate_if_needed():
-    """
-    Check schema version and run migration if needed.
-    Called during application startup.
-    """
-    from .version import SCHEMA_VERSION
-    from .migration import run_full_migration
-
-    db_version = get_db_schema_version()
-
-    if db_version == SCHEMA_VERSION:
-        print(f"Schema version {SCHEMA_VERSION} matches. Fast startup.")
-        # Still ensure tables exist (they should if version matches)
-        init_db()
-        return
-
-    if db_version is None:
-        print(f"No schema version found. Running initial migration (v{SCHEMA_VERSION})...")
-    else:
-        print(f"Schema mismatch: DB has v{db_version}, code expects v{SCHEMA_VERSION}")
-        print("Running full migration...")
-
-    try:
-        # Set schema version BEFORE migration so a crash mid-migration
-        # doesn't cause an infinite re-migration loop on every restart.
-        init_db()
-        set_db_schema_version(SCHEMA_VERSION)
-
-        success = run_full_migration(geocode=False)
-
-        if success:
-            print(f"Migration complete. Schema version {SCHEMA_VERSION}.")
-        else:
-            print("Warning: Migration completed but no data was imported.")
-
-    except Exception as e:
-        print(f"FATAL: Migration failed: {e}")
-        print("Application cannot start. Please check database and CSV files.")
-        raise
-