Replace TinyDB with a Postgres

[max-tet]

• Add postgres to the docker-compose stack
• Use psycopg3
• Write SQL
• refactor all database objects and operations
• migrate existing database to Postgres on startup
  • Make a backup of the tinyDB database before
  • Only do this if it was not done before
• Make unit tests work again and make them fast by reusing the application and just truncating tables between tests where possible

Database Patterns

Look at https://github.com/FreeshardBase/freeshard-controller/tree/main/freeshard-controller-backend/freeshard_controller/db for examples. Copy what is needed.

• All functions take AsyncConnection as their first param — the caller is responsible for connection lifecycle.
• Use db_conn() context manager from connection.py to get a connection from the pool.
• Row-to-model mapping uses cursor(row_factory=class_row(PydanticModel)).
• SQL is written inline as f-strings with parameterized values (psycopg %(name)s style placeholders). Type-annotate SQL strings as LiteralString where possible.
• Dynamic SQL construction (for variable columns in UPDATE/INSERT) is built from Pydantic model_dump() keys.
• Explicit await conn.commit() is needed when autocommit is off (most service-layer callers commit explicitly).