Add field-level aria-errormessage, aria-invalid, and aria-describedby across the TFE form

WCAG 3.3.1 (Error Identification): failing fields now get
aria-errormessage pointing to the flash-error container and
aria-invalid="true". WCAG 3.3.3 (Error Suggestion): <small>
hint text on inputs, selects, and file fields is now linked via
aria-describedby (always, not just on error).

Changes:
- text-field.php, select-field.php, checkbox-list.php: accept
  $errorFieldName; add aria-errormessage/aria-invalid on match;
  add id to <small> and aria-describedby on the control
- fieldset-tfe-info.php: aria-invalid on synopsis textarea
- fichiers-fragment.php: aria-describedby on cover, note
  d'intention, TFE, annexes, and website inputs; aria-invalid
  on format checkboxes when error matches 'formats'
- form.php: id="flash-error" + tabindex="-1" on flash-error
  div; accept $errorFieldName from callers
- admin/add.php: set $errorFieldName, wire $withAutofocusFn
  (was identity default)
- admin/edit.php: set $errorFieldName
- partage/index.php: consume autofocus field, wire autofocus
  function, add App::flashAutofocus() in submit catch block

Also fixes WCAG standards issue: removed invalid 'required'
HTML attribute from <fieldset> elements in checkbox-list.php
and fichiers-fragment.php (only aria-required stays). Added
role="group" for explicit ARIA semantics.

app/templates/partials/form/fichiers-fragment.php

@@ -35,6 +35,7 @@ $selectedFormats = isset($_POST['formats']) && is_array($_POST['formats'])
 
 $adminMode = ($_POST['admin_mode'] ?? '0') === '1';
 $editMode  = ($_POST['edit_mode'] ?? '0') === '1';
+$errorFieldName = $errorFieldName ?? null;
 
 // TFE file is optional when format is Site web (3), Performance (4) or Installation (6)
 $noTfeFileFormats = [3, 4, 6];
@@ -53,8 +54,8 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
     <legend>Format(s)</legend>
     <div>
         <span class="admin-row-label">Format(s) du TFE :<?= !$adminMode ? ' <span class="asterisk">*</span>' : '' ?></span>
-        <fieldset class="admin-checkbox-group"
-                  <?= !$adminMode ? 'required aria-required="true"' : '' ?> >
+        <fieldset class="admin-checkbox-group" role="group"
+                  <?= !$adminMode ? 'aria-required="true"' : '' ?> >
             <legend class="sr-only">Format(s) du TFE</legend>
             <ul>
                 <?php foreach ($allFormats as $opt): ?>
@@ -63,7 +64,8 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
                         <input type="checkbox"
                                name="formats[]"
                                value="<?= htmlspecialchars((string)$opt['id']) ?>"
-                               <?= in_array((int)$opt['id'], $selectedFormats, true) ? 'checked' : '' ?>>
+                               <?= in_array((int)$opt['id'], $selectedFormats, true) ? 'checked' : '' ?>
+                               <?= ($errorFieldName === 'formats') ? 'aria-invalid="true" aria-errormessage="flash-error" aria-describedby="flash-error"' : '' ?>>
                         <?= htmlspecialchars($opt['name']) ?>
                     </label>
                 </li>
@@ -85,8 +87,9 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
                    name="queue_file[cover][]"
                    class="tfe-file-picker tfe-file-picker--single"
                    data-queue-type="cover"
-                   data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForCover ?? []), ENT_QUOTES) ?>'>
-            <small>JPG, PNG ou WEBP. Format 4:3 recommandé. Max 20 MB.</small>
+                   data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForCover ?? []), ENT_QUOTES) ?>'
+                   aria-describedby="couverture-hint">
+            <small id="couverture-hint">JPG, PNG ou WEBP. Format 4:3 recommandé. Max 20 MB.</small>
         </div>
         <?php if ($editMode): ?>
         <button type="button" class="btn btn--sm btn--ghost file-browser-trigger"
@@ -111,8 +114,10 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
                    class="tfe-file-picker tfe-file-picker--single"
                    data-queue-type="note_intention"
                    data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForNoteIntention ?? []), ENT_QUOTES) ?>'
-                   <?= !$adminMode ? 'required' : '' ?>>
-            <small>PDF uniquement. Max 100 MB. Si votre fichier est trop lourd, compressez-le avec <a href="https://www.bentopdf.com" target="_blank" rel="noopener">bentopdf.com</a>.</small>
+                   <?= !$adminMode ? 'required' : '' ?>
+                   <?= ($errorFieldName === 'note_intention') ? 'aria-invalid="true" aria-errormessage="flash-error"' : '' ?>
+                   aria-describedby="note_intention-hint<?= ($errorFieldName === 'note_intention') ? ' flash-error' : '' ?>">
+            <small id="note_intention-hint">PDF uniquement. Max 100 MB. Si votre fichier est trop lourd, compressez-le avec <a href="https://www.bentopdf.com" target="_blank" rel="noopener">bentopdf.com</a>.</small>
         </div>
         <?php if ($editMode): ?>
         <button type="button" class="btn btn--sm btn--ghost file-browser-trigger"
@@ -138,8 +143,10 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
                    class="tfe-file-picker"
                    data-queue-type="tfe"
                    <?= (!$adminMode && !$tfeFileOptional) ? 'required' : '' ?>
-                   data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForTfe ?? []), ENT_QUOTES) ?>'>
-            <small class="admin-file-hint">
+                   data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForTfe ?? []), ENT_QUOTES) ?>'
+                   <?= ($errorFieldName === 'tfe-files-input') ? 'aria-invalid="true" aria-errormessage="flash-error"' : '' ?>
+                   aria-describedby="tfe-files-hint<?= ($errorFieldName === 'tfe-files-input') ? ' flash-error' : '' ?>">
+            <small id="tfe-files-hint" class="admin-file-hint">
                 Glissez pour réordonner.
                 <br>
                 <br>
@@ -175,8 +182,9 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
                        multiple
                        class="tfe-file-picker"
                        data-queue-type="annexe"
-                       data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForAnnexe ?? []), ENT_QUOTES) ?>'>
-                <small class="admin-file-hint">PDF ou archives ZIP/TAR. Max 1 GB. Glissez pour réordonner.</small>
+                       data-existing-files='<?= htmlspecialchars(json_encode($existingFilesJsonForAnnexe ?? []), ENT_QUOTES) ?>'
+                       aria-describedby="annexe-files-hint">
+                <small id="annexe-files-hint" class="admin-file-hint">PDF ou archives ZIP/TAR. Max 1 GB. Glissez pour réordonner.</small>
             </div>
             <?php if ($editMode): ?>
             <button type="button" class="btn btn--sm btn--ghost file-browser-trigger"
@@ -199,8 +207,9 @@ $websiteLabel = htmlspecialchars($_POST['website_label'] ?? '');
         <div class="admin-file-input">
             <input type="url" id="website_url" name="website_url"
                    value="<?= $websiteUrl ?>"
-                   placeholder="https://mon-tfe.erg.be">
-            <small>Le TFE sera affiché comme un site embarqué sur sa page publique.</small>
+                   placeholder="https://mon-tfe.erg.be"
+                   aria-describedby="website_url-hint">
+            <small id="website_url-hint">Le TFE sera affiché comme un site embarqué sur sa page publique.</small>
         </div>
     </div>