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/Dockerfile

@@ -0,0 +1,13 @@
+# Multi-stage: build the static site with Hugo, serve it with nginx.
+# Build context is site/ only — legal pages are pre-generated (build-legal.sh)
+# and committed, and screenshots are copied in by collect_screenshots.sh, so no
+# other part of the repo is needed at image-build time.
+FROM hugomods/hugo:exts-0.140.2 AS build
+WORKDIR /src
+COPY . .
+RUN hugo --minify --gc
+
+FROM nginx:alpine
+COPY nginx.conf /etc/nginx/conf.d/default.conf
+COPY --from=build /src/public /usr/share/nginx/html
+EXPOSE 80