feat(admin): refresh usage and show Codex reset credits

[mikehostetler]

Summary

Provider usage is now a live operational view. The Incant dashboard reloads on a bounded interval, shows quota windows with relative reset times, and keeps the table focused on the fields needed to select an account.

Codex accounts also show read-only reset-credit availability and the next credit expiry. A failed optional credit-detail request does not hide the normal quota data or credit count.

Key behavior

• Adds an Incant router helper that polls only the open Provider Usage dashboard. The default page interval is one minute and supports a configured range of 15 seconds through one hour.
• Keeps page polling separate from upstream provider refreshes. A page reload does not make a provider request.
• Shows account availability, remaining quota, reset time, reset-credit count, and credit expiry in one compact table.
• Uses strict response validation and bounded credential refreshes for Codex usage data.
• Keeps reset-credit support read-only. No reset-credit consumption action is exposed.
• Uses Req timeout options that are compatible with the active Finch adapter.

Validation

• mix ci: 505 tests passed, 9 excluded.
• Manually validated the dashboard with a live Codex OAuth account.
• Confirmed the configured polling interval and navigation cleanup in LiveView tests.

Related: #15