Applied the decision-first diagnostic surface IA contract to EnvironmentDiagnostics and SupportDiagnostics bundles. Added recommended_first_check and separated technical metadata as per Spec 373.
## Summary
- consolidate internal platform naming from `Tenant` to `Environment` / `ManagedEnvironment` across models, controllers, services, and Filament resources
- rename environment-scoped UI surfaces such as dashboards, chooser flows, navigation, and related widgets to match the updated environment-first domain language
- align middleware, onboarding/review lifecycle services, jobs, and route/context controllers with the new environment-scoped architecture
## Validation
- not rerun as part of this commit/push/PR request
## Notes
- branch is 1 commit ahead of `platform-dev`
- main commit: `refactor: consolidate internal tenant model naming`
Co-authored-by: Ahmed Darrazi <ahmed.darrazi@live.de>
Reviewed-on: #355
