css: replace admin-form-row/admin-label/admin-input/select/textarea classes with semantic selectors

Remove five presentational classes from admin forms and replace with
structural CSS selectors scoped to .admin-form:

- .admin-form-row  → .admin-form > div:not(.admin-submit-wrap)
  Grid layout (260px label col + 1fr input col) applied directly to div
  children of the form; submit-wrap div excluded via :not().

- .admin-label     → .admin-form > div:not(.admin-submit-wrap) > label
  Scoped to the direct label child of each form row div; does not bleed
  into nested checkbox labels inside .admin-checkbox-list.

- .admin-input / .admin-select / .admin-textarea
  → .admin-form input:not([type=checkbox|radio|file|hidden|submit])
  → .admin-form select
  → .admin-form textarea
  Also extended to .admin-inline-form input/select (tags page) so the
  tags table inputs retain identical base styling and focus colour.

Templates updated: add.php, edit.php, login.php, account.php,
pages-edit.php, import.php, tags.php,
templates/partials/form/jury-fieldset.php — all class= attributes for
the five removed classes stripped.

import.php: added 'admin-form' class alongside 'admin-import-area' so
its single file-input row gets the grid row treatment; submit div was
already using admin-submit-wrap so it is correctly excluded.

No visual change — selectors target the same elements as before.

templates/partials/form/jury-fieldset.php

@@ -33,18 +33,18 @@ $juryIdx = max(count($juryLecteurs), 1);
             <legend>Composition du jury</legend>
 
             <!-- Président·e -->
-            <div class="admin-form-row">
-                <label class="admin-label" for="jury_president">Président·e :</label>
-                <input class="admin-input" type="text" id="jury_president" name="jury_president"
+            <div>
+                <label for="jury_president">Président·e :</label>
+                <input type="text" id="jury_president" name="jury_president"
                        value="<?= htmlspecialchars($juryPresident ?? '') ?>"
                        placeholder="Nom du/de la président·e (interne)">
             </div>
 
             <!-- Promoteur·ice -->
-            <div class="admin-form-row">
-                <label class="admin-label" for="jury_promoteur">Promoteur·ice :</label>
+            <div>
+                <label for="jury_promoteur">Promoteur·ice :</label>
                 <div class="admin-jury-row">
-                    <input class="admin-input" type="text" id="jury_promoteur" name="jury_promoteur"
+                    <input type="text" id="jury_promoteur" name="jury_promoteur"
                            value="<?= htmlspecialchars($juryPromoteur ?? '') ?>" placeholder="Nom">
                     <label class="admin-checkbox-label admin-jury-ext">
                         <input type="checkbox" name="jury_promoteur_ext" value="1"
@@ -54,13 +54,13 @@ $juryIdx = max(count($juryLecteurs), 1);
             </div>
 
             <!-- Lecteur·ices (dynamic list) -->
-            <div class="admin-form-row">
-                <label class="admin-label">Lecteur·ices :</label>
+            <div>
+                <label>Lecteur·ices :</label>
                 <div>
                     <div id="jury-lecteurs-list" class="admin-jury-list">
                         <?php if (empty($juryLecteurs)): ?>
                         <div class="admin-jury-entry">
-                            <input class="admin-input" type="text" name="jury_lecteurs[]" placeholder="Nom">
+                            <input type="text" name="jury_lecteurs[]" placeholder="Nom">
                             <label class="admin-checkbox-label admin-jury-ext">
                                 <input type="checkbox" name="jury_lecteurs_ext[0]" value="1"> Externe
                             </label>
@@ -70,7 +70,7 @@ $juryIdx = max(count($juryLecteurs), 1);
                         <?php else: ?>
                             <?php foreach ($juryLecteurs as $li => $lm): ?>
                             <div class="admin-jury-entry">
-                                <input class="admin-input" type="text" name="jury_lecteurs[]"
+                                <input type="text" name="jury_lecteurs[]"
                                        value="<?= htmlspecialchars($lm['name']) ?>" placeholder="Nom">
                                 <label class="admin-checkbox-label admin-jury-ext">
                                     <input type="checkbox" name="jury_lecteurs_ext[<?= $li ?>]" value="1"
@@ -93,7 +93,7 @@ $juryIdx = max(count($juryLecteurs), 1);
             var list = document.getElementById('jury-lecteurs-list');
             var div  = document.createElement('div');
             div.className = 'admin-jury-entry';
-            div.innerHTML = '<input class="admin-input" type="text" name="jury_lecteurs[]" placeholder="Nom">'
+            div.innerHTML = '<input type="text" name="jury_lecteurs[]" placeholder="Nom">'
                           + '<label class="admin-checkbox-label admin-jury-ext">'
                           + '<input type="checkbox" name="jury_lecteurs_ext[' + juryIdx + ']" value="1"> Externe'
                           + '</label>'