* 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
