feat(asset): add asset categorization support #298

Summary

Add the canonical two-level asset taxonomy to pyoaev so producers (collectors, custom integrations) can classify endpoints with the new categorization fields introduced in OpenAEV, instead of free-form strings.

Changes

• New pyoaev.asset_types module exposing AssetCategory, AssetSubCategory, CloudProvider and AssetCriticality as str enums, exported from the package root.
• EndpointManager: make endpoint_platform / endpoint_arch (and endpoint_hostname) optional with asset_name as the only required attribute, and add the optional categorization / cloud fields (asset_category, asset_subcategory, asset_criticality, asset_internet_facing, asset_cloud_provider, asset_cloud_native_type, asset_cloud_region, asset_metadata, endpoint_url).

Context

Dependency of OpenAEV-Platform/openaev#6452 (asset categorization). The SDK enums mirror the backend taxonomy so producers send backend-aligned values on the wire.