Update frontend to use new backend API:
- save_config now accepts optional 'activate' parameter
- activate endpoint now requires 'type' parameter ('system' | 'user')
When switching to managed mode, call activate with type='system' instead
of deleting user config, so custom configurations are preserved for
future use.
Move type imports to @/types/sandbox-provider instead of re-exporting
from service file. Remove unnecessary retry:0 options to use React
Query's default retry behavior.
Replace manual fetch calls in use-sandbox-provider.ts with typed ORPC
contracts and client. Adds type definitions to types/sandbox-provider.ts
and registers contracts in the console router for consistent API handling.