feat(ml): add database schema, config parser, and DVC setup

- Initialize DVC with local storage backend (task 1.6)
- Create PostgreSQL schema for training_runs table (task 1.7)
- Add SQLAlchemy database connection setup (task 1.8)
- Create Pydantic config models for pipeline.yaml (task 2.1)
- Add migration runner for database setup
- Fix pyproject.toml package discovery config

services/ml/app/__init__.py

@@ -0,0 +1 @@
+"""ML service application package."""