a11y: WCAG 2.5.5 target sizes + 2.5.3 label-in-name fixes

Increase touch/click target sizes to meet WCAG 2.5.5 (minimum 44×44px
for navigation, 32px for admin UI controls):

- main.css / search.css: pagination buttons 2rem → min-height/min-width
  2.75rem (44px). Changed display to inline-flex for proper centering.
- admin.css: .admin-btn-sm gains min-height: 2rem (32px) and switches
  to inline-flex so the constraint is respected.
- admin.css: .admin-btn-remove (jury ✕ buttons) gains min-height: 2rem
  and inline-flex display + explicit cursor:pointer.

WCAG 2.5.3 label-in-name — jury remove buttons already had aria-label;
wrap the visible ✕ glyph in <span aria-hidden='true'> so screen readers
hear only the aria-label, not the symbol:

- templates/partials/form/jury-fieldset.php: all three ✕ occurrences
  (static PHP blocks + JS-generated innerHTML string) wrapped.

WCAG 4.1.2 / semantic HTML:
- admin/index.php: add role='toolbar' aria-label='Actions groupées' to
  the bulk-actions bar.

public/admin/index.php

@@ -133,7 +133,7 @@ document.addEventListener('DOMContentLoaded', () => {
     </form>
 
     <!-- Bulk actions bar -->
-    <div id="bulk-actions" class="admin-bulk-actions">
+    <div id="bulk-actions" class="admin-bulk-actions" role="toolbar" aria-label="Actions groupées">
         <strong><span id="selected-count">0</span> TFE(s) sélectionné(s)</strong>
         <div class="admin-bulk-btns">
             <button type="button" class="admin-btn-sm admin-btn-publish" onclick="bulkAction('publish')">Publier</button>