fix(webapp): stage the per-queue Redis depth; stop seeders full-reloading the dashboard

- the seeder now stages the email-sends QUEUE counter (what the watch checks
  and queue pages read) alongside the env-level one — a drain watch on the
  stand no longer one-shots against an empty live counter
- vite ignores seed-*.mts: editing or running a seeder was full-reloading
  every open dashboard tab every few seconds

Author: kathiekiwi