Moves system-level operations (auth, billing, admin) to use the
/metadata endpoint instead of /graphql.
This cleans up the endpoint separation so /graphql is purely for core
objects (Company, People, etc.) and /metadata handles all system
operations.
Part of prep work for webhook/API key core migration.
## Context
#4774
## How was it tested
Locally
## In further PRs
- Update connection status upon page change
- Adapt Info banner to dark mode
- placeholders for form