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

package.json

@@ -8,13 +8,11 @@
     "node": "24.x"
   },
   "dependencies": {
-    "@forevolve/bootstrap-dark": "^2.1.0",
     "@fortawesome/fontawesome-free": "^5.15.4",
-    "ajax-bootstrap-select": "^1.4.5",
+    "@popperjs/core": "^2.11.8",
     "autocompleter": "^6.1.2",
     "autoprefixer": "^10.4.0",
-    "bootstrap": "^4.6.1",
-    "bootstrap-select": "^1.13.18",
+    "bootstrap": "^5.3.8",
     "clipboard": "^2.0.8",
     "cssnano": "^5.0.13",
     "easymde": "^2.21.0",
@@ -27,12 +25,11 @@
     "gulp-sourcemaps": "^3.0.0",
     "gulp-uglify": "^3.0.2",
     "html5sortable": "^0.13.3",
-    "jquery": "^3.6.0",
     "konami": "^1.7.0",
     "moment": "^2.29.4",
-    "popper.js": "^1.16.1",
     "postcss": "^8.5.26",
     "sass": "^1.103.1",
+    "tom-select": "^2.6.2",
     "uglify-js": "^3.14.5"
   },
   "devDependencies": {