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

RIGS/templates/rigboard.html

@@ -4,29 +4,27 @@
 {% block content %}
 <div class="row align-items-center justify-content-between py-2 align-middle">
     <div class="col-sm-12 col-md align-middle d-flex flex-wrap">
-        Key: <span class="table-success mr-1 px-2 rounded">Ready</span><span
-            class="table-warning mr-1 px-2 rounded text-nowrap">Action Required</span><span
-            class="table-danger mr-1 px-2 rounded text-nowrap">Needs MIC</span><span
-            class="table-secondary mr-1 px-2 rounded">Cancelled</span><span
+        <span class="me-2">Key:</span><span class="table-success me-1 px-2 rounded">Ready</span><span
+            class="table-warning me-1 px-2 rounded text-nowrap">Action Required</span><span
+            class="table-danger me-1 px-2 rounded text-nowrap">Needs MIC</span><span
+            class="table-secondary me-1 px-2 rounded">Cancelled</span><span
             class="table-info px-2 rounded text-nowrap">Non-Rig</span>
     </div>
-    {% if perms.RIGS.add_event %}
-    <div class="col text-right">
+    <div class="col-12 col-md-auto d-flex flex-wrap justify-content-end gap-2 mt-2 mt-md-0">
+        {% if perms.RIGS.add_event %}
         {% button 'new' 'event_create' %}
+        {% endif %}
+        {% if not request.GET.legacy %}
+        {% if not request.GET.hide_cancelled %}
+        <a href="?hide_cancelled=true" class="btn btn-primary">Hide cancelled</a>
+        {% else %}
+        <a href="." class="btn btn-primary">Show cancelled</a>
+        {% endif %}
+        <a href="?legacy=true" class="btn btn-secondary">Legacy rigboard</a>
+        {% else %}
+        <a href="." class="btn btn-secondary">New rigboard</a>
+        {% endif %}
     </div>
-    {% endif %}
-    {% if not request.GET.legacy %}
-
-    {% if not request.GET.hide_cancelled %}
-    <a href="?hide_cancelled=true" class="btn btn-primary mr-3">Hide cancelled</a>
-    {% else %}
-    <a href="." class="btn btn-primary mr-3">Show cancelled</a>
-    {% endif %}
-
-    <a href="?legacy=true" class="btn btn-secondary">Legacy rigboard</a>
-    {% else %}
-    <a href="." class="btn btn-secondary">New rigboard</a>
-    {% endif %}
 </div>
 
 {% if request.GET.legacy %}