Import lists from CSV or text and match each entry

The list editor gets an Import button. A .csv/.tsv/.txt file or pasted
text is parsed on the server: header columns (Title, Year, Artist or
Director, Note, Rank), numbered lines and trailing "(1999)" years are
understood, and Canon's own export round-trips.

Each row is then searched with the list's provider and scored. A row is
matched automatically only when one result fits exactly and nothing else
fits as well; a year or artist in the file breaks ties, an exact title
beats a bracketed version like "(Live)", and "Artist - Title" lines are
tried both ways. Custom lists need a year or subtitle to be certain.
Everything else is shown for review with a recommended pick, the other
results, "Add as written", Skip, and a search-again box. Entries are
added in file order after the existing ones, with any notes from the
file.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/templates/pages/admin_list.html

@@ -13,6 +13,7 @@
     </div>
     <div class="admin-head-actions">
       <a class="btn btn--ghost" data-bind="public" href="/l/{{.Data.List.Slug}}">{{icon "external"}}View</a>
+      <button class="btn btn--ghost" type="button" data-action="import" title="Add entries from a CSV or text file">{{icon "upload"}}Import</button>
       {{template "export" .Data.List.Slug}}
       {{if ne $c.Key "custom"}}<button class="btn btn--ghost" type="button" data-action="refresh-all" title="Pull the latest details and artwork from each entry's source">{{icon "refresh"}}Refresh all</button>{{end}}
       <button class="btn" type="button" data-action="edit-list">{{icon "settings"}}List settings</button>