Port creature parsing for map packets to Python

[hjubi]

Motivation

• Restore the C# creature-parsing path in the Python map packet parser so creature details (name, hp, vocation, etc.) are preserved instead of being reduced to plain object IDs.
• Provide storage and domain objects to hold parsed creature data so map packets can reference creatures by id and tests can inspect full creature state.

Description

• Added python/tibia_api/creatures.py implementing Creature and CreatureStorage and exported them from tibia_api via __init__.py.
• Extended Client (python/tibia_api/client.py) with creature_storage and player to support creature lifecycle operations.
• Expanded NetworkMessage (python/tibia_api/network_message.py) with primitive readers (read_uint32, read_bool, read_string), appearance helpers (read_creature_outfit, read_mount_outfit), a full read_creature_instance implementation, and integrated creature handling into read_field so 0x61/0x62/0x63 markers produce Creature entries and map object references use data=creature.id.
• Implemented map packet scaffolding and utilities: packets/ (base.py, map_updates.py), world_map.py, position.py, and constants.py to support parsing and map state updates.
• Added unit test test_read_field_parses_creature_payload to python/tests/test_map_updates.py that exercises parsing of an UnknownCreature map field and asserts parsed creature fields and storage insertion.

Testing

• Ran unit test suite PYTHONPATH=python python3 -m unittest discover -s python/tests -v and all tests succeeded (including the new test_read_field_parses_creature_payload).
• Performed an ad-hoc end-to-end parse of a FullMap packet containing an embedded creature and verified the NetworkMessage.parsed_creatures contained the expected creature id and name.

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Codex Task