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.

todo/01-css-semantic-refactor.md

@@ -42,7 +42,7 @@
 - [ ] **`add.php`/`edit.php`**: Replace `<div class="admin-alert admin-alert--error/--success">` with `<p role="alert">` / `<p role="status">`
 - [ ] **`index.php`**: Replace `<div class="admin-stats">` / `<div class="admin-stat">` children with `<dl>/<dt>/<dd>`
 - [ ] **`index.php`**: Replace `<div class="admin-maintenance-bar">` with `<aside role="status">` or `<p role="status">`
-- [ ] **`index.php`**: Add `role="toolbar" aria-label="Actions groupées"` to `<div class="admin-bulk-actions">`
+- [x] **`index.php`**: Add `role="toolbar" aria-label="Actions groupées"` to `<div class="admin-bulk-actions">`
 - [ ] **`index.php`**: Add `scope="col"` to all `<th>` cells in the admin table
 - [ ] **`index.php`**: Add non-colour indicator + `aria-label="Statut : …"` to status badge `<span>` elements
 - [ ] **`tags.php`**: Add `scope="col"` to `<th>` cells