Bootstrap 5 & remove jQuery (#661)

* build: move frontend assets to Bootstrap 5.3 and Tom Select

* feat: migrate templates and scripts to Bootstrap 5, dropping jQuery

Templates
- Rename Bootstrap 4 classes and data attributes (data-bs-*, ms-/me-/ps-/pe-,
  text-start/end, form-group -> mb-3, input-group wrappers removed, badges,
  custom controls -> form-check/form-select, media -> d-flex, btn-close, ...)
- Dark mode now uses Bootstrap 5.3 colour modes (data-bs-theme on <html>),
  set from <head> to avoid a flash of the light theme
- Remove the Bootstrap 4 /bootstrap/ demo page
- Contextual table classes (table-success etc.) still work as plain
  backgrounds for the rigboard key

JavaScript
- Remove jQuery: src.js/interaction.js and every inline template script are
  rewritten in plain JS on top of small helpers (helpers.js, bundled with
  Bootstrap into jpop.js so inline scripts can use them)
- Replace bootstrap-select/ajax-bootstrap-select with Tom Select. The remote
  search now sends the `q` parameter and reads `text`, which is what the
  API actually uses (the old picker sent `term` and read `label`)
- HTML fragments are fetched with an X-Requested-With header so views keep
  rendering their modal variants, and fetched scripts are re-executed
- Remove the Bootstrap 4 plugin script includes

* fix: stop rigboard header buttons stretching to full width under Bootstrap 5

* fix: restore dark-mode brand colours and contextual table colours under Bootstrap 5

* fix: brighten dark-mode links and make coloured card outlines visible

* fix: calendar layout and grid borders, navbar search button width, guard missing modal links

* fix: readable text in dark-mode Tom Select inputs and placeholders, restore form-control column widths

* build: split the Dockerfile into cached stages with prod and dev targets

* deploy: make compose.yml development-only with live reload, and document it

* fix: keep badge text colour for links inside badges

* fix: restore table-bordered grid lines in dark mode

* fix: include Bootstrap's progress styles and keep progress labels readable

versioning/templates/activity_feed.html

@@ -3,20 +3,18 @@
 <script>
   const matches = window.matchMedia("(prefers-reduced-motion: reduce)").matches || window.matchMedia("(update: slow)").matches;
   //TODO Maybe this should be a reduce rather than remove
-  dur = matches ? 0 : 'slow';
-  $(document).ready(function() {
-    $(function () {
-        $( "#activity" ).hide();
-        $( "#activity" ).load( "{% url 'activity_feed' %}", function() {
-          $('#activity_loading').slideUp(dur,function(){
-              $('#activity').slideDown(dur);
-          });
-            const whiteList = $.fn.tooltip.Constructor.Default.whiteList;
-            whiteList.ins = []
-          whiteList.del = []
-          $('#activity [data-toggle="popover"]').popover({whiteList: whiteList});
-        });
-    });
+  dur = matches ? 0 : 600;
+  ready(function() {
+    var activity = document.getElementById('activity');
+    var loading = document.getElementById('activity_loading');
+    activity.style.display = 'none';
+    ajaxFetch("{% url 'activity_feed' %}")
+      .then(function (response) { return response.text(); })
+      .then(function (html) {
+        setHtml(activity, html);
+        slideUp(loading, dur);
+        window.setTimeout(function () { slideDown(activity, dur); }, dur);
+      });
   });
 </script>
 {% endblock %}
@@ -26,7 +24,7 @@
   <div class="list-group list-group-flush">
     <div id="activity_loading" class="list-group-item text-center">
       <div class="spinner-border text-primary" role="status">
-         <span class="sr-only">Loading...</span>
+         <span class="visually-hidden">Loading...</span>
       </div>
     </div>
     <div id="activity">