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

templates/partials/button.html

@@ -3,9 +3,9 @@
 {% elif pk %}
 <a href="{% url target pk %}" class="btn {{ class }}" {% if id %}id="{{id}}"{%endif%} {% if style %}style="{{style}}"{%endif%} {% if text == 'Print' %}target="_blank"{%endif%}><span class="fas {{ icon }} align-middle"></span> <span class="d-none d-sm-inline align-middle">{{ text }}</span></a>
 {% elif copy %}
-<button class="btn btn-secondary btn-sm mr-1" data-clipboard-target="{{id}}" data-content="Copied to clipboard!"><span class="fas fa-copy"></span></button>
+<button class="btn btn-secondary btn-sm me-1" data-clipboard-target="{{id}}" data-bs-content="Copied to clipboard!"><span class="fas fa-copy"></span></button>
 {% elif today %}
-<button class="btn btn-info col-sm-2" onclick="var date = new Date(); $('#{{id}}').val([date.getFullYear(), ('0' + (date.getMonth()+1)).slice(-2), ('0' + date.getDate()).slice(-2)].join('-'))" tabindex="-1" type="button">Today</button>
+<button class="btn btn-info col-sm-2" onclick="document.getElementById('{{id}}').value = new Date().getISOString()" tabindex="-1" type="button">Today</button>
 {% else %}
 <a href="{% url target %}" class="btn {{ class }}" {% if id %}id="{{id}}"{%endif%} {% if style %}style="{{style}}"{%endif%}><span class="fas {{ icon }} align-middle"></span> <span class="d-none d-sm-inline align-middle">{{ text }}</span></a>
 {% endif %}