Add noindex pages, robots.txt and operator footer

- Page.noindex: marked pages get a robots meta tag and a Disallow line in the
  generated robots.txt (single source of truth in src/pages.py)
- templates/robots.txt: public pages indexable, noindex pages and data files not
- Footer shows an optional operator line from contents/snippets/footer_operator.md
- Tests for robots.txt, noindex meta and footer

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

templates/html/page.html

@@ -4,6 +4,9 @@
     <meta charset="utf-8">
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <title>50Ω – lär dig amatörradio</title>
+    {% if robots %}
+    <meta name="robots" content="{{ robots }}">
+    {% endif %}
     {% if social_image %}
     <meta property="og:type" content="website">
     <meta property="og:site_name" content="50Ω">
@@ -153,8 +156,7 @@
                     Inte godkänd av DARC eller SSA.
                   </div>
                   <div class="fiftyohm-footer-links d-flex gap-2">
-                    {# TODO: The operator must add their own imprint / contact details and privacy information here. #}
-                    <span class="text-secondary">[Utgivare, kontakt och integritetspolicy &ndash; ska fyllas i av driftansvarig]</span>
+                    {% if footer_operator %}<span class="text-secondary">{{ footer_operator }}</span>{% endif %}
                   </div>
                 </div>
               </div>

templates/robots.txt

@@ -0,0 +1,11 @@
+# robots.txt – generated by the site generator, do not edit by hand.
+# The course pages may be crawled and indexed. Pages with contact details may not.
+
+User-agent: *
+Allow: /
+{% for page in noindex_pages -%}
+Disallow: /{{ page }}
+{% endfor -%}
+# Data files (search indexes etc.) are not pages
+Disallow: /*.json$
+Disallow: /*.zip$