Refactor: consolidate duplicate DbtCloudRunStatus enum

[stumelius]

Refactor

DbtCloudRunStatus is defined three times with inconsistent types:

• dbt_cloud/command/run/list.py — Enum with string values + as_number() method
• dbt_cloud/command/run/get.py — IntEnum with numeric values
• dbt_cloud/command/run/cancel.py — IntEnum with numeric values

Fix: Define a single canonical DbtCloudRunStatus (probably in dbt_cloud/command/run/__init__.py or a shared module) and import it everywhere.