New /leaderboards route (linked from the More menu): aggregates kind-9735
receipts into top-zapped spots and top supporters, with week/month/all-time
tabs. Reuses the batched zap helpers. Also hardens the deploy smoke test to
boot lazy routes (/, /leaderboards, /bounties), since route chunks can fail
independently.
SortDropdown offered 'Most Zapped' but MapPage's sort switch had no zaps case,
so picking it silently fell back to newest-first. Adds a batched useZapTotals
hook (ONE receipt query for every location) and implements the sort.