[BUG] Extra-usage balance on claude.ai/settings/usage does not update without page refresh

Summary

On the claude.ai settings/usage page, the quota gauges (Q5h, Q7d) update dynamically via ajax, but the extra-usage credit balance does not. The dollar amount remains stale until the user manually refreshes the page.

Impact

When a user crosses 100% Q5h and enters extra-usage billing:

• The quota gauge correctly shows 100% (live update)
• The extra-usage balance appears unchanged because it doesn't refresh
• The user has no real-time indication that credits are being consumed
• By the time they notice (manual refresh or next page load), significant extra-usage charges may have accumulated

Community report from @przadka on #41930: extra_usage.used_credits went from $56.66 → $83.94 (+$27.28) between two API checks, with no visible change on the web UI.

Steps to Reproduce

1. Use Claude Code on a Max plan until Q5h reaches 100%
2. Continue working (extra-usage billing activates)
3. Observe claude.ai/settings/usage — quota gauge shows 100% but the extra-usage dollar amount does not change
4. Refresh the page — the balance jumps to reflect actual spend

Expected Behavior

The extra-usage balance should update dynamically (same ajax pattern as the quota gauges), especially since this is the moment users most need real-time cost visibility.

Related

• #41930 — przadka's data showing the mismatch
• #47512 — broader auth/frontend dependency issues