feat(speedtest): full speedtest-tracker-style automation (2.9.0)

Switch worker to the Ookla CLI (jitter, packet loss, server, ISP,
shareable result URL, bytes). Migration 028 enriches speedtest_results
+ adds a generic app_settings store. New /speedtest page: KPIs,
throughput + latency charts, window stats, configurable schedule
(reschedulable cron) & low-speed alert threshold, history table.
SV card gains ping/jitter + a link through to the page.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/router.js

@@ -33,6 +33,7 @@ const ROUTES = [
   { name: 'mirror',    re: /^\/mirror$/,    keys: [] },
   { name: 'settings', re: /^\/settings$/, keys: [] },
   { name: 'jobs', re: /^\/jobs$/, keys: [] },
+  { name: 'speedtest', re: /^\/speedtest$/, keys: [] },
   { name: 'home',     re: /^\/?$/,                 keys: [] }
 ];