ccs-balance: Sync cc-switch Balance and DSH Session Usage Statistics

The `ccs-balance` plugin provides DSH with a unified balance, usage, and session monitoring view. It supports provider balance queries with multi-currency and exchange-rate conversion, multi-dimensional token statistics (daily/monthly/total), and session cost tracking. Users can access the data via a sidebar entry, with in-panel scrolling supported. The plugin retrieves real-time data from the cc-switch database and API, falling back to pricing-based estimates when data is missing, thereby significantly reducing the time spent querying data across systems.