- Rewrite database.py with asyncpg pool-based DatabasePool class
- Support named params (:param) → positional ($N) conversion
- Transaction context manager using contextvars for connection reuse
- Replace all SQLAlchemy query building with raw SQL in routes and sql modules
- Update utils/db.py to use raw SQL strings instead of SQLAlchemy Select
- Update utils/db_init.py to use local engine creation for DDL only
- Update all test files to use string table names and raw SQL
- Remove databases and sqlalchemy-stubs from dependencies
- Keep sqlalchemy only for schema.py definitions and alembic migrations
