fix: Load .env file for dbt database credentials

dbt uses env_var() in profiles.yml to read POSTGRES_PASSWORD,
but subprocess.run() doesn't automatically load .env files.
Added python-dotenv to load credentials before dbt runs.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

scripts/data/load_toronto_data.py

@@ -28,6 +28,11 @@ from datetime import date
 from pathlib import Path
 from typing import Any
 
+from dotenv import load_dotenv
+
+# Load .env file so dbt can access POSTGRES_* environment variables
+load_dotenv()
+
 # Add project root to path
 PROJECT_ROOT = Path(__file__).parent.parent.parent
 sys.path.insert(0, str(PROJECT_ROOT))