feat(web): tane.comunes.org landing + localized app screenshots

- Hugo site (site/): EN/ES intro + legal (generated from docs/legal), an
  ES/EN About page from docs/{que-es-tane,what-is-tane}.md, seed-green theme,
  responsive header, store-badge placeholders, multi-stage Hugo->nginx image.
- Golden screenshot harness (test/screenshots/): en,es,fr,de,pt,ja + RTL demo,
  real fonts via DejaVu Sans + FontManifest; skip-by-default tag so CI stays
  green. collect_screenshots.sh feeds site/ and fastlane phoneScreenshots.
- Drop editorial notes from the public explainer.

site/layouts/_default/list.html

@@ -0,0 +1,15 @@
+{{ define "main" }}
+<section class="doc doc-list">
+  <h1>{{ .Title }}</h1>
+  <p class="lead">{{ T "legalIntro" }}</p>
+  <ul class="legal-index">
+    {{ range .Pages.ByWeight }}
+    <li>
+      <a href="{{ .RelPermalink }}">{{ .Title }}</a>
+      {{ with .Description }}<span class="desc">{{ . }}</span>{{ end }}
+    </li>
+    {{ end }}
+  </ul>
+  <p class="crumb"><a href="{{ "/" | relLangURL }}">← {{ T "backToHome" }}</a></p>
+</section>
+{{ end }}