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/co2.pug

@@ -0,0 +1,12 @@
+- function g(v) { return v != null ? v.toFixed(4)+' g CO₂' : '—'; }
+
+div(class='bg-white border border-gray-200 rounded-xl p-5')
+  h2(class='text-base font-semibold mb-4') Sustainability & CO₂
+  if job.co2_per_page_view == null
+    p(class='text-sm text-gray-400') No CO₂ data collected.
+  else
+    div(class='grid grid-cols-2 sm:grid-cols-4 gap-3')
+      each item in [['Per page view', job.co2_per_page_view], ['Total', job.co2_total], ['First-party', job.co2_first_party], ['Third-party', job.co2_third_party]]
+        div(class='metric-card text-center')
+          div(class='text-lg font-bold text-green-700')= g(item[1])
+          div(class='text-xs text-gray-500 mt-1')= item[0]