Extract Spark rate limit windows from the Codex usage response and expose
them as spark_session/spark_weekly quotas, reusing the existing prefix
mechanism. Map codex quota types to readable dashboard labels.
Fixes#3431
Add read-only GET to inspect per-credit reset inventory (status, granted,
expiry, remaining) with a Quota Tracker modal. DRY the route via shared
connection/refresh helpers; keep existing consume POST unchanged.
Co-authored-by: Cursor <cursoragent@cursor.com>