Port pytoyoda's authentication and read-only data flow to a Go builtin
plugin behind the existing plugin contract. Implements the three-legged
ForgeRock/OAuth2 login (authenticate callback loop, authorize, token
exchange), silent refresh with full re-auth fallback, and the full
Toyota gateway header set with backoff on 429/5xx.
Exposes read-only capabilities: vehicles, telemetry, location, health,
status, electric, notifications, and service-history. Config takes a
MyToyota email/password and a Toyota/Lexus brand select.
Europe-only and read-only, matching pytoyoda's limitations.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
