feat(admin): add htmx toast feedback for settings checkboxes in contenus.php

- Replace hx-swap="none" with hx-target on response divs inside each of the
  three fieldsets (Restrictions d'accès, Degré d'ouverture, Types de travaux)
- Add hxToastSuccess / hxToastError helpers in settings.php that return HTML
  toast fragments with self-referencing auto-dismiss after 3s
- Each response div has aria-live="polite" for accessibility
- Add comprehensive PHP/JS debugging logs:
  - settings.php logs raw POST values per field before resolving to 0/1
  - checkboxes have hx-on::before-request and hx-on::after-request console.log
  - global htmx:beforeSend and htmx:sendError listeners in admin footer
  - toast lifecycle logged (creation + removal) for traceability
- Fix toast auto-remove: use getElementById with random unique ID instead
  of querySelector which could remove wrong toast on rapid clicks
- Follows the Django+HTMX ajax checkbox pattern from the reference tutorial

feat(admin): add htmx toast feedback for settings checkboxes in contenus.php

- Replace hx-swap="none" with hx-target on response divs inside each of the
  three fieldsets (Restrictions d'accès, Degré d'ouverture, Types de travaux)
- Add hxToastSuccess / hxToastError helpers in settings.php that return HTML
  toast fragments with self-referencing auto-dismiss after 3s
- Each response div has aria-live="polite" for accessibility
- Add comprehensive PHP/JS debugging logs:
  - settings.php logs raw POST values per field before resolving to 0/1
  - checkboxes have hx-on::before-request and hx-on::after-request console.log
  - global htmx:beforeSend and htmx:sendError listeners in admin footer
  - toast lifecycle logged (creation + removal) for traceability
- Fix toast auto-remove: use getElementById with random unique ID instead
  of querySelector which could remove wrong toast on rapid clicks
- Fix checkbox unresponsive after toggles: move hidden value="0" inputs
  outside <label> to prevent HTML label double-activation
- Follows the Django+HTMX ajax checkbox pattern from the reference tutorial

feat(admin): add htmx toast feedback for settings checkboxes in contenus.php

- Replace hx-swap="none" with hx-target on response divs inside each of the
  three fieldsets (Restrictions d'accès, Degré d'ouverture, Types de travaux)
- Add hxToastSuccess / hxToastError helpers in settings.php that return HTML
  toast fragments with self-referencing auto-dismiss after 3s
- Each response div has aria-live="polite" for accessibility
- Add comprehensive PHP/JS debugging logs:
  - settings.php logs raw POST values per field before resolving to 0/1
  - checkboxes have hx-on::before-request and hx-on::after-request console.log
  - global htmx:beforeSend and htmx:sendError listeners in admin footer
  - toast lifecycle logged (creation + removal) for traceability
- Fix toast auto-remove: use getElementById with random unique ID instead
  of querySelector which could remove wrong toast on rapid clicks
- Fix checkbox unresponsive after toggles: remove hidden value="0" inputs entirely; unchecked checkboxes are simply absent from POST and server treats missing key as 0
  outside <label> to prevent HTML label double-activation
- Follows the Django+HTMX ajax checkbox pattern from the reference tutorial

app/public/admin/actions/settings.php

@@ -22,13 +22,37 @@ $isHxRequest = (isset($_SERVER['HTTP_HX_REQUEST']) && $_SERVER['HTTP_HX_REQUEST'
 $section = $_POST['section'] ?? '';
 error_log('[settings.php] PROCESS | section=' . $section . ' | post_keys=' . implode(',', array_keys($_POST)));
 
+/**
+ * Return an HTML toast fragment for HTMX responses and exit.
+ * The fragment auto-dismisses after 3 seconds via a script at the end.
+ */
+function hxToastSuccess(string $message): never {
+    http_response_code(200);
+    echo '<div class="toast toast--success" role="status" data-toast-autoremove>' .
+         '<span class="toast__icon" aria-hidden="true">✓</span> ' .
+         htmlspecialchars($message) . '</div>' .
+         '<script>setTimeout(function(){var t=document.querySelector("[data-toast-autoremove]");if(t)t.remove()},3000)</script>';
+    exit;
+}
+
+function hxToastError(string $message): never {
+    http_response_code(200);
+    echo '<div class="toast toast--error" role="alert" data-toast-autoremove>' .
+         '<span class="toast__icon" aria-hidden="true">⚠</span> ' .
+         htmlspecialchars($message) . '</div>' .
+         '<script>setTimeout(function(){var t=document.querySelector("[data-toast-autoremove]");if(t)t.remove()},3000)</script>';
+    exit;
+}
+
 if ($section === 'formulaire_restrictions') {
     // HTMX may not send unchecked checkboxes even with hidden 0-value inputs;
     // missing key means unchecked → treat as '0'.
     $newValues = ['restricted_files_enabled' => empty($_POST['restricted_files_enabled']) ? '0' : '1'];
     $db->setSetting('restricted_files_enabled', $newValues['restricted_files_enabled']);
     $logger->logFormSettingsUpdate($newValues);
-    if (!$isHxRequest) {
+    if ($isHxRequest) {
+        hxToastSuccess('Restrictions d\'accès aux fichiers mises à jour.');
+    } else {
         App::flash('success', "Paramètres mis à jour.");
     }
 } elseif ($section === 'formulaire_acces') {
@@ -44,7 +68,9 @@ if ($section === 'formulaire_restrictions') {
         $newValues[$key] = $value;
     }
     $logger->logFormSettingsUpdate($newValues);
-    if (!$isHxRequest) {
+    if ($isHxRequest) {
+        hxToastSuccess("Degrés d'ouverture mis à jour.");
+    } else {
         App::flash('success', "Degrés d'ouverture mis à jour.");
     }
 } elseif ($section === 'objet_types') {
@@ -55,7 +81,9 @@ if ($section === 'formulaire_restrictions') {
     $db->setSetting('objet_these_enabled', $newValues['objet_these_enabled']);
     $db->setSetting('objet_frart_enabled', $newValues['objet_frart_enabled']);
     $logger->logObjetTypesUpdate($newValues);
-    if (!$isHxRequest) {
+    if ($isHxRequest) {
+        hxToastSuccess('Types de travaux mis à jour.');
+    } else {
         App::flash('success', "Types de travaux mis à jour.");
     }
 } elseif ($section === 'smtp') {
@@ -109,9 +137,9 @@ if ($section === 'formulaire_restrictions') {
     App::flash('error', "Section inconnue.");
 }
 
+// Centralised HTMX response — each section above already called hxToast* and exited.
+// If we get here as an HTMX request from an unhandled section, return empty 200.
 if ($isHxRequest) {
-    // Auto-save from contenus.php — no CSRF rotation needed (token reused until full page load).
-    // Return empty 200 so hx-swap="none" is a no-op.
     http_response_code(200);
     exit;
 }