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/app.js

@@ -31,7 +31,8 @@ const VIEWS = {
   links:           () => import('./views/links.js'),
   mirror:          () => import('./views/mirror.js'),
   settings:        () => import('./views/settings.js'),
-  jobs:            () => import('./views/jobs.js')
+  jobs:            () => import('./views/jobs.js'),
+  speedtest:       () => import('./views/speedtest.js')
 };
 
 async function renderView(ctx) {