Add billing provider resource type and clean plugin registry

[cobycloud]

Summary

• add a billing provider resource type constant and use it in the billing provider base class
• register the cipher suites namespace in the interface registry for discovery
• remove swarmauri_core and swarmauri_base references from the plugin citizenship registry

Testing

• uv run --directory pkgs/base --package swarmauri-base ruff format .
• uv run --directory pkgs/base --package swarmauri-base ruff check . --fix
• uv run --directory pkgs/swarmauri --package swarmauri ruff format .
• uv run --directory pkgs/swarmauri --package swarmauri ruff check . --fix

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https://chatgpt.com/codex/tasks/task_e_68f14018b8b883268bb510bb9b1160ca