Watch EPIRent version and archive its download packages

- Poll the public download page for "Aktuelle Version <nr> vom <date>",
  report changes through the normal change feed and notification mail,
  and show the current version as a card on the overview. Runs on its own
  interval (default 30 min); the first run only records a baseline.
- Archive epirentServer.zip / epirentClient.zip per version number so we
  keep a download cache and history: streamed to disk with SHA-256 and
  size, fetched in a background thread so ticket polling is unaffected,
  with a free-space check before downloading (~1.1 GB per version).
- Retention is configurable via EPIRENT_DOWNLOAD_KEEP, where 0 means
  unlimited; a successful archive is reported as a change and by mail.
- New Downloads page listing the archived versions with checksums and
  links to fetch the cached files.
- Notification lines now omit the arrow when there is no previous value
  and drop the "#" for entries without a ticket.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

templates/_macros.html

@@ -2,9 +2,11 @@
   <li class="{{ 'unseen' if not c.seen else '' }}"
       {% if c.detail %}title="{{ c.detail }}"{% endif %}>
     <span class="tag tag-{{ c.field }}">{{ c.label }}</span>
-    <a class="cnum" href="{{ url_for('ticket_detail', ticket_id=c.ticket_id) }}">#{{ c.ticket_number }}</a>
+    {% if c.ticket_id %}
+      <a class="cnum" href="{{ url_for('ticket_detail', ticket_id=c.ticket_id) }}">#{{ c.ticket_number }}</a>
+    {% endif %}
     <span class="ctitle">{{ c.ticket_title }}</span>
-    <span class="cchg">{{ c.old_value or '–' }} → <b>{{ c.new_value or '–' }}</b></span>
+    <span class="cchg">{% if c.old_value %}{{ c.old_value }} → {% endif %}<b>{{ c.new_value or '–' }}</b></span>
     <time>{{ c.detected_at|dt }}</time>
     {% if not c.seen %}
       <form method="post" action="{{ url_for('mark_one_read', change_id=c.id) }}" class="mark-one">

templates/base.html

@@ -13,6 +13,7 @@
       <a href="{{ url_for('index') }}">Übersicht</a>
       <a href="{{ url_for('analytics_view') }}">Auswertung</a>
       <a href="{{ url_for('changes') }}">Änderungen</a>
+      <a href="{{ url_for('downloads_view') }}">Downloads</a>
       <a href="{{ url_for('new_ticket_form') }}">+ Neues Ticket</a>
       <a href="{{ zammad_url }}" target="_blank" rel="noopener">Zammad&nbsp;↗</a>
     </nav>

templates/downloads.html

@@ -0,0 +1,41 @@
+{% extends "base.html" %}
+{% block title %}Downloads · EPI-Support{% endblock %}
+{% block content %}
+
+<section class="panel">
+  <div class="panel-head">
+    <h2>EPIRent Download-Archiv</h2>
+    {% if current %}
+      <span class="hint-inline">aktuelle Version: <b>{{ current.version }}</b> vom {{ current.released_at }}</span>
+    {% endif %}
+  </div>
+
+  {% if versions %}
+    {% for v in versions %}
+      <div class="dl-version">
+        <div class="dl-head">
+          <span class="dl-ver">Version {{ v.version }}</span>
+          <span class="dl-meta">{{ human(v.total) }} · gesichert am {{ v.downloaded_at|dt }}</span>
+        </div>
+        <ul class="dl-files">
+          {% for f in v.files %}
+            <li>
+              <a href="{{ url_for('download_file', version=v.version, filename=f.filename) }}">⬇ {{ f.filename }}</a>
+              <span class="dl-size">{{ human(f.size) }}</span>
+              {% if f.sha256 %}<code class="dl-hash" title="SHA-256">{{ f.sha256[:16] }}…</code>{% endif %}
+            </li>
+          {% endfor %}
+        </ul>
+      </div>
+    {% endfor %}
+    {% if keep and keep > 0 %}
+      <p class="hint">Es werden die letzten <b>{{ keep }}</b> Versionsstände aufbewahrt; ältere werden automatisch gelöscht.</p>
+    {% else %}
+      <p class="hint">Aufbewahrung: <b>unbegrenzt</b> – es wird nichts automatisch gelöscht (ca. 1,1 GB je Stand).</p>
+    {% endif %}
+  {% else %}
+    <p class="muted">Noch keine Pakete archiviert. Der Poller lädt sie im Hintergrund,
+      sobald eine Version bekannt ist (ca. 1,1 GB pro Stand – das dauert einen Moment).</p>
+  {% endif %}
+</section>
+{% endblock %}

templates/index.html

@@ -9,6 +9,12 @@
   <div class="card {{ 'alert' if stats.unseen else '' }}">
     <span class="num">{{ stats.unseen }}</span><span class="lbl">ungelesene Änderungen</span>
   </div>
+  {% if epirent_version %}
+  <div class="card">
+    <span class="num">{{ epirent_version.version }}</span>
+    <span class="lbl">EPIRent-Version<br>vom {{ epirent_version.released_at }}</span>
+  </div>
+  {% endif %}
   <div class="card status">
     {% if last_run %}
       <span class="num {{ 'ok' if last_run.status == 'ok' else 'err' }}">