Add pagination/search/sort to the admin tables that can grow large

Uses simple-datatables (vanilla JS, no jQuery needed) on the Users,
Sessions, Email Log, and Feedback tables, since those grow with real
usage. Left Games (small, admin-curated) and Hints (row order is
meaningful - "checked in order" - a sortable column would mislead)
untouched.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

templates/game/admin/sessions/index.html.twig

@@ -9,7 +9,7 @@
     </div>
 
     <div style="background: #fff; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,.07); overflow: hidden;">
-        <table style="width: 100%; min-width: 700px; border-collapse: collapse; font-size: 0.9rem;">
+        <table class="admin-datatable" style="width: 100%; min-width: 700px; border-collapse: collapse; font-size: 0.9rem;">
             <thead>
                 <tr style="background: #f1f5f9; border-bottom: 1px solid #e2e8f0;">
                     <th style="padding: 0.75rem 1rem; text-align: left; color: #475569; font-weight: 600;">ID</th>