* Block start/restart/rebuild/update APIs while Supervisor is not fully running
Supervisor boots apps and Home Assistant Core in a specific order, and
replays a similarly ordered sequence while restoring a backup (during
which it is in the freeze state). Calling start/restart/rebuild/update
via the API while one of those sequences is still in progress risks
running it out of order, or blocking a scheduled start from that
sequence outright via job concurrency.
Add a require_running_system decorator that rejects these API calls
unless Supervisor is fully started (CoreState.RUNNING), and apply it to:
- App start/restart/rebuild (fixes#7189) and update
- Home Assistant Core start/restart/rebuild/update
- Plugin (audio/dns/multicast) restart/update, and cli/observer update
Also add a translatable APISystemNotReadyError so the API returns a
clean, user-facing message and error_key instead of leaking the
technical JobConditionException message.
* Address review: neutral error wording + require_running_system test coverage
- Reword APISystemNotReadyError so it no longer implies the block is only
due to startup, since the same guard also applies while frozen for a
backup restore.
- Add tests/api/test_require_running_system.py covering the rejection path
(400 + system_not_ready_error, business logic not invoked) for app
start/restart/rebuild, app update via the store API, Core
start/restart/rebuild/update, and all plugin update/restart routes,
parametrized across SETUP/STARTUP/FREEZE.
* Simplify APISystemNotReadyError message wording
* Switch status code to 503
