fix: enhance billing operations and session management in API

CHANGELOG.md

@@ -10,6 +10,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 
 - **More reliable service health reporting.** The backend health check no longer falsely reports the service as unhealthy after sustained traffic. Previously, an internal counter grew over time and would eventually cross a fixed threshold — even under normal load — causing orchestrators to unnecessarily restart the service.
 - **Lower resource usage under load.** The backend now uses a single shared connection to Redis instead of opening dozens of separate ones. Previously, each rate limiter and internal component created its own connection pool, which could waste resources and risk hitting connection limits during heavy traffic.
+- **More reliable billing operations.** Billing actions like changing your plan, cancelling, and viewing invoices now benefit from the same automatic session refresh, request tracing, and error handling as the rest of the app. Previously, these used a separate internal path that could fail silently if your session expired mid-action.
+- **Session list now correctly highlights your current session.** The active sessions list in settings now properly identifies which session you're currently using. Previously, the "current session" marker never appeared due to an internal mismatch in how sessions were identified.
 
 ## [0.12.0-alpha] - 2026-03-01