Add notes list and integrate into templates

New partial templates/notes-list.html to render the notes list.
Add .notes-list CSS for styling and ensure contents areas use it.
Refactor site.hs: add loadNoteLinks and provide a "notes" listField
used by index and note pages.

templates/notes-list.html

@@ -0,0 +1,7 @@
+<ul class="notes-list">
+    $for(notes)$
+    <li>
+        <a href="$url$">$title$</a>
+    </li>
+    $endfor$
+</ul>