feat(security): implement session management features including idle timeout, keepalive, and secure logout

includes/footer.php

@@ -16,6 +16,49 @@
 <!-- Fociz Agenda Notificaties Engine -->
 <script src="/assets/js/notifications.js"></script>
 
+<?php
+$sessionIdleTimeout = function_exists('get_session_idle_timeout') ? get_session_idle_timeout() : 1800;
+?>
+<!-- Fociz Inactiviteitswaarschuwing Modal (ISO 27001 / NIST SP 800-63B) -->
+<div id="focizSessionModal" class="fixed inset-0 z-[9999] bg-slate-950/80 backdrop-blur-md hidden items-center justify-center p-4">
+    <div class="bg-white dark:bg-[#111622] border border-amber-500/30 dark:border-amber-500/30 rounded-3xl w-full max-w-md shadow-2xl p-6 sm:p-7 text-center relative overflow-hidden">
+        <div class="w-14 h-14 rounded-2xl bg-amber-500/10 dark:bg-amber-500/20 border border-amber-500/30 text-amber-600 dark:text-amber-400 flex items-center justify-center mx-auto mb-4">
+            <svg class="w-7 h-7 animate-pulse" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z"></path>
+            </svg>
+        </div>
+
+        <h3 class="text-lg font-bold text-slate-900 dark:text-white tracking-tight mb-2">
+            Sessie verloopt bijna
+        </h3>
+        
+        <p class="text-xs text-slate-500 dark:text-slate-400 mb-5 leading-relaxed">
+            Wegens inactiviteit wordt u binnenkort automatisch afgemeld conform het beveiligingsbeleid. Klik op <strong class="text-slate-800 dark:text-slate-200">Blijf Ingelogd</strong> om uw sessie te verlengen.
+        </p>
+
+        <div class="inline-flex items-center space-x-2 px-4 py-2 rounded-2xl bg-amber-50 dark:bg-amber-950/30 border border-amber-200 dark:border-amber-800/60 text-amber-700 dark:text-amber-300 font-mono text-xs font-bold mb-6">
+            <svg class="w-4 h-4 text-amber-500" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                <circle cx="12" cy="12" r="10" stroke-width="2"></circle>
+                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 6v6l4 2"></path>
+            </svg>
+            <span>Verloopt over:</span>
+            <span id="focizSessionCountdown" class="text-amber-600 dark:text-amber-400 font-black tracking-wider">02:00</span>
+        </div>
+
+        <div class="grid grid-cols-2 gap-3">
+            <button type="button" id="focizSessionLogoutBtn" class="w-full py-2.5 px-4 rounded-xl bg-slate-100 hover:bg-slate-200 dark:bg-slate-800 dark:hover:bg-slate-700 text-slate-700 dark:text-slate-300 text-xs font-semibold transition cursor-pointer">
+                Nu Uitloggen
+            </button>
+            <button type="button" id="focizSessionKeepaliveBtn" class="w-full py-2.5 px-4 rounded-xl bg-indigo-600 hover:bg-indigo-500 text-white text-xs font-bold transition shadow-xs cursor-pointer">
+                Blijf Ingelogd
+            </button>
+        </div>
+    </div>
+</div>
+
+<!-- Fociz Session Guard Script (NIST SP 800-63B / ISO 27001) -->
+<script src="/assets/js/session-guard.js" data-timeout="<?= $sessionIdleTimeout ?>"></script>
+
 <script>
     // Lucide Icons initialiseren
     if (typeof lucide !== 'undefined') {