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/note.html

@@ -11,6 +11,7 @@ $partial("templates/head.html")$
                 that are big enough -->
         <div id="contents-big">
             <p class="mini-header">Notes <a id="up-arrow" href="/">←</a></p>
+            $partial("templates/notes-list.html")$
             <p class="mini-header">Contents <a id="up-arrow" href="#">↑</a></p>
             $toc$
         </div>
@@ -38,4 +39,4 @@ $partial("templates/head.html")$
     </div>
 </body>
 
-</html>
+</html>