v0.1.19

Added - Diagnostic entities and improved URL discovery

• Diagnostic sensor entities — the companion integration now creates
  diagnostic entities: Auth Status, Cameras Discovered, Addon Version,
  Addon Uptime, and Last Snapshot time
• Improved addon URL discovery — both config flow and runtime URL
  resolver now use HA's built-in get_addons_info/async_get_addon_info
  instead of raw HTTP calls to the Supervisor API