add UUID support in dialect; enhance tests for Mapped[uuid.UUID] beha…

[h0rn3t]

This pull request improves support for the UUID type in the psqlpy-sqlalchemy dialect, ensuring that SQLAlchemy models annotated with Mapped[uuid.UUID] are handled correctly and that the dialect returns Python uuid.UUID objects instead of strings. It also bumps the package version to 0.1.1b2 and adds a targeted test to verify this behavior.

UUID type support improvements:

• Added explicit mapping for sqltypes.Uuid to the internal _PGUUID handler in the PSQLPyAsyncDialect class, ensuring that columns annotated as Mapped[uuid.UUID] are returned as uuid.UUID objects.
• Added a new test (test_uuid_mapped_annotation_without_explicit_as_uuid) to verify that the dialect returns uuid.UUID objects for models using the Mapped[uuid.UUID] annotation pattern, without needing explicit UUID(as_uuid=True).
• Updated test imports in tests/test_uuid_support.py to include Mapped and mapped_column, supporting the new test case.

Version bump:

• Updated the package version to 0.1.1b2 in both pyproject.toml and psqlpy_sqlalchemy/__init__.py. [1] [2]…vior