Add "last updated" to stats page

- inferred by looking at last updated collections
- may be wrong if "add collection" was used, but should work fine most times

server/app.py

@@ -405,9 +405,11 @@ def force_refresh_collection(collection_id: int):
 @flask_app.route("/stats")
 def show_stats():
     elements: List[MediaElement] = MediaElement.select()
+    collections: List[MediaCollection] = MediaCollection.select()
     return render_template(
         "stats.htm",
         stats={
+            "last_updated": orm.max(c.last_updated for c in collections),
             "media": {
                 "known": orm.count(elements),
                 "known_seconds": orm.sum(m.length for m in elements),

server/templates/stats.htm

@@ -11,6 +11,9 @@
         {{ macros.body_header() }}
         <h1>{{ title }}</h1>
         <ul>
+            <li>
+                Last updated: {{ stats.last_updated }}
+            </li>
             {% set cats = (
                 ("Known", stats.media.known, stats.media.known_seconds),
                 ("Watched", stats.media.watched, stats.media.watched_seconds),