Add no purge, manual delete options (#12)

- Add htmx, hx attributes
- Only add/update items since last check
- Move messages to session to persist across redirects
- Polish styles a bit (still WIP)

src/public/user/log-on.php

@@ -18,7 +18,7 @@ $isSingle = SECURITY_MODEL == Security::SINGLE_USER_WITH_PASSWORD;
 page_head('Log On'); ?>
 <h1>Log On</h1>
 <article>
-    <form method=POST action=/user/log-on hx-post=/user/log-on><?php
+    <form method=POST action=/user/log-on><?php
         if (($_GET['returnTo'] ?? '') != '') { ?>
             <input type=hidden name=returnTo value="<?=$_GET['returnTo']?>"><?php
         }