Polish admin and stats tab styling

Improve tab border handling and spacing for admin and stats views, plus minor copy spacing fixes.

public/control.html

@@ -569,7 +569,7 @@
             <div class="d-flex flex-wrap align-items-end justify-content-between gap-2 mb-2">
               <div class="info-line small text-muted">
                 <span class="badge bg-light text-dark border" aria-hidden="true">i</span>
-                <span class="info-text"><span id="admin-users-count">—</span> utilisateur(s)</span>
+                <span class="info-text"><span id="admin-users-count" class="me-1">—</span>utilisateur(s)</span>
               </div>
               <div class="d-flex gap-2">
                 <button type="button" id="open-add-user-modal" class="btn btn-warning btn-sm btn-compact">Ajouter un utilisateur</button>