Add admin console with login, dashboard, content/config/plugin/user management

File-based admin panel accessible at /admin.php with:
- Session-based auth with bcrypt hashing and brute-force protection
- Dashboard with site statistics and quick actions
- Content manager: browse, create, edit, delete files
- Config editor with JSON validation
- Plugin overview with status indicators
- User management: add, remove, change passwords
- CSRF protection on all forms, path traversal prevention
- Updated README (NL/EN) and guides with admin documentation

admin-console/templates/pages/plugins.php

@@ -0,0 +1,44 @@
+<h2 class="mb-4"><i class="bi bi-plug"></i> Plugins</h2>
+
+<?php if (empty($plugins)): ?>
+    <div class="alert alert-info">Geen plugins gevonden in de plugins map.</div>
+<?php else: ?>
+    <div class="row g-4">
+        <?php foreach ($plugins as $plugin): ?>
+            <div class="col-md-6">
+                <div class="card shadow-sm">
+                    <div class="card-header d-flex justify-content-between align-items-center">
+                        <strong><i class="bi bi-plug"></i> <?= htmlspecialchars($plugin['name']) ?></strong>
+                        <?php if ($plugin['enabled']): ?>
+                            <span class="badge bg-success">Actief</span>
+                        <?php else: ?>
+                            <span class="badge bg-secondary">Inactief</span>
+                        <?php endif; ?>
+                    </div>
+                    <div class="card-body">
+                        <table class="table table-sm mb-0">
+                            <tr>
+                                <td class="text-muted">Hoofdbestand</td>
+                                <td>
+                                    <?= $plugin['has_main'] ? '<i class="bi bi-check-circle text-success"></i> Aanwezig' : '<i class="bi bi-x-circle text-danger"></i> Ontbreekt' ?>
+                                </td>
+                            </tr>
+                            <tr>
+                                <td class="text-muted">Configuratie</td>
+                                <td>
+                                    <?= $plugin['has_config'] ? '<i class="bi bi-check-circle text-success"></i> Aanwezig' : '<i class="bi bi-dash-circle text-muted"></i> Geen' ?>
+                                </td>
+                            </tr>
+                            <tr>
+                                <td class="text-muted">README</td>
+                                <td>
+                                    <?= $plugin['has_readme'] ? '<i class="bi bi-check-circle text-success"></i> Aanwezig' : '<i class="bi bi-dash-circle text-muted"></i> Geen' ?>
+                                </td>
+                            </tr>
+                        </table>
+                    </div>
+                </div>
+            </div>
+        <?php endforeach; ?>
+    </div>
+<?php endif; ?>