fix: series list view sorts by name instead of sort field

In series_list(), the SQLite query correctly orders results by
Series.sort, but a subsequent Python sorted() call (needed to
re-order after appending the "None" category entry) was using
Series.name as the sort key instead of Series.sort.

This caused series titles with leading articles (A, An, The) to
sort strictly alphabetically by the article rather than by the
meaningful word, e.g. "A Collins-Burke Mystery" appeared under
"A" instead of "C".

Fix by using Series.sort (with a fallback to Series.name if sort
is NULL) as the key in the Python re-sort, consistent with the
intent of the existing DB query.

Fixes #3583

cps/web.py

@@ -1026,7 +1026,7 @@ def series_list():
                             .count())
             if no_series_count:
                 entries.append([db.Category(_("None"), "-1"), no_series_count])
-            entries = sorted(entries, key=lambda x: x[0].name.lower(), reverse=not order_no)
+            entries = sorted(entries, key=lambda x: (x[0].sort or x[0].name).lower(), reverse=not order_no)
             return render_title_template('list.html',
                                          entries=entries,
                                          folder='web.books_list',