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/components/sidebar.js

@@ -122,6 +122,7 @@ export function renderSidebar(root) {
     el('div', { class: 'sb-section' },
       el('div', { class: 'sb-title' }, 'Navigate'),
       navItem('Sacred Valley', '/sacred-valley'),
+      navItem('Speedtest', '/speedtest'),
       navItem('Terminal', '/terminal'),
       navItem('Search', '/search'),
       inboxItem,