rename .html templates to .jinja2 for more consistency

templates/backlinks.jinja2

@@ -0,0 +1,27 @@
+{% extends "base.html" %}
+
+{% block title %}Pages linking to “{{ p.title }}” - {{ app_name }}{% endblock %}
+
+{% block meta %}
+<meta name="robots" content="noindex,nofollow" />
+{% endblock %}
+
+{% block content %}
+<h1 id="firstHeading">{{ p.title }}</h1>
+<div class="preview-subtitle">{{ T('backlinks') }}</div>
+
+{% if backlinks %}
+<ul>
+{% for op in backlinks %}
+  <li><a href="{{ op.get_url() }}">
+    {{ op.title }} (<strong>#{{ op.id }}</strong>)
+  </a></li>
+{% endfor %}
+</ul>
+{% else %}
+<p class="placeholder">{{ T("backlinks-empty") }}</p>
+{% endif %}
+
+<p>{{ T("back-to") }} <a href="{{ p.get_url() }}">{{ p.title }}</a>.</p>
+{% endblock %}
+