Accounts table sorting, grouping, and summaries

We improved the accounts overview and table to make large lists easier to scan. You can now sort and group accounts, see summary rows and total payouts, expand sections with more reliable state handling, and spot a subtle horizontal scroll hint for wide tables.

In practice, this means cleaner grouping in the overview, faster scanning of totals in the table, and fewer surprises when expanding or collapsing account sections during analysis.