feat: initial Speedboard implementation

sitespeed.io web UI with Express/Pug/SQLite — port 3132.
Includes job queue, SSE live log, full metrics dashboard,
site history, CO2/axe/CWV sections, and Docker support.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

views/partials/axe.pug

@@ -0,0 +1,15 @@
+- function num(v) { return v != null ? v : '—'; }
+- const hasAxe = job.axe_critical != null || job.axe_serious != null
+
+div(class='bg-white border border-gray-200 rounded-xl p-5')
+  h2(class='text-base font-semibold mb-4') Accessibility (axe)
+  if !hasAxe
+    p(class='text-sm text-gray-400') No axe data collected.
+  else
+    div(class='grid grid-cols-2 sm:grid-cols-4 gap-3')
+      each item in [['Critical', job.axe_critical, 'bg-red-50 border-red-300 text-red-700'], ['Serious', job.axe_serious, 'bg-orange-50 border-orange-300 text-orange-700'], ['Moderate', job.axe_moderate, 'bg-yellow-50 border-yellow-300 text-yellow-700'], ['Minor', job.axe_minor, 'bg-blue-50 border-blue-300 text-blue-700']]
+        div(class=`metric-card border ${item[2]} text-center`)
+          div(class='text-2xl font-bold')= num(item[1])
+          div(class='text-xs mt-1')= item[0]
+    if job.axe_critical === 0 && job.axe_serious === 0
+      p(class='text-sm text-green-600 mt-3 font-medium') No critical or serious violations found.