Port upstream 0.55.0: refresh spend on provider updates

[Finesssee]

Summary

• port upstream CodexBar v0.55.0 Usage & Spend publication/invalidation behavior from fix(spend): silent refresh and invalidation coverage steipete/CodexBar#3106
• silently refresh the open Usage & Spend pane when provider snapshots publish updates
• debounce provider-update bursts so one multi-provider refresh does not trigger one dashboard rebuild per event
• strengthen the backend summary cache revision with limit/balance/currency and exact daily spend points

Upstream evidence

• target release: v0.55.0
• upstream commit: 6538ac345 / fix(spend): silent refresh and invalidation coverage steipete/CodexBar#3106

Validation

• cargo test --manifest-path apps/desktop-tauri/src-tauri/Cargo.toml usage_spend --no-fail-fast -> compile/test pass
• focused rustfmt and git diff --check -> pass
• frontend Vitest remains blocked locally by the existing pnpm/Corepack shim failure; hosted CI/final frontend gate must exercise the listener path

Scope

Usage & Spend refresh/invalidation only. No provider-auth or version bump changes.

[Finesssee]

Thermo-nuclear re-review

Previous finding is closed: initial/manual and silent provider-update refreshes now share one summary-fetch function with explicit visible vs silent state behavior. TypeScript no-emit typecheck passes when using the repository-installed dependency tree.

Verdict: APPROVED.