Make Jauge, Onglets, and every form-field widget real native Bulma elements

- Jauge now renders a real <progress class="progress"> instead of a hand-built pair of absolutely-positioned divs. The bas/haut color interpolation still works, set via Bulma's own --bulma-progress-value-background-color CSS custom property rather than fighting the class.
- Onglets' tab strip is now genuine Bulma tabs markup (tabs > ul > li, is-active on the li) instead of custom forgeTabBar/forgeTabBtn classes; forgeShowTab (duplicated in screen_edit.html and play.html) now toggles is-active to match.
- Champ texte/email/mot de passe get class="input", Zone de texte gets class="textarea", Case à cocher/Bouton radio's existing <label> wrapper gets class="checkbox"/"radio" (Bulma's own convention — the structure already matched, just needed the class), Liste déroulante is wrapped in Bulma's required <div class="select"> (a bare class on the <select> itself has zero effect in Bulma), Tableau gets class="table is-bordered is-fullwidth" with the per-cell inline borders removed so Bulma's own table styling applies.
- Removed the now-dead .forgeTabBar/.forgeTabBtn CSS.

Updated tests/test_jauge.py and tests/test_onglets_widget.py assertions to match the new markup (value="X" attribute instead of width:X% inline style, --bulma-progress-value-background-color instead of background-color, forgeShowTab(this) marker instead of the removed forgeTabBtn class) — same behavior, different rendering mechanism. Full suite green (89 passed), verified end to end against the real "test" project via the actual /play route.

templates/play.html

@@ -82,7 +82,7 @@
     var groupId = btn.dataset.tabBtn;
     var targetId = btn.dataset.tabTarget;
     document.querySelectorAll('[data-tab-btn="' + groupId + '"]').forEach(function (b) {
-      b.classList.toggle('active', b === btn);
+      b.classList.toggle('is-active', b === btn);
     });
     document.querySelectorAll('[data-tab-group="' + groupId + '"]').forEach(function (p) {
       p.style.display = (p.id === targetId) ? '' : 'none';

templates/screen_edit.html

@@ -758,7 +758,7 @@ function forgeShowTab(btn) {
   var groupId = btn.dataset.tabBtn;
   var targetId = btn.dataset.tabTarget;
   document.querySelectorAll('[data-tab-btn="' + groupId + '"]').forEach(function (b) {
-    b.classList.toggle('active', b === btn);
+    b.classList.toggle('is-active', b === btn);
   });
   document.querySelectorAll('[data-tab-group="' + groupId + '"]').forEach(function (p) {
     p.style.display = (p.id === targetId) ? '' : 'none';