release(v2.2.0): add storage explorer + disk usage scanner

public/api/admin/diskUsageSummary.php

@@ -0,0 +1,41 @@
+<?php
+// public/api/admin/diskUsageSummary.php
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../../config/config.php';
+require_once PROJECT_ROOT . '/src/models/DiskUsageModel.php';
+
+if (session_status() !== PHP_SESSION_ACTIVE) {
+    session_start();
+}
+
+header('Content-Type: application/json; charset=utf-8');
+
+$authenticated = !empty($_SESSION['authenticated']);
+$isAdmin       = !empty($_SESSION['isAdmin']) || (!empty($_SESSION['admin']) && $_SESSION['admin'] === '1');
+
+if (!$authenticated || !$isAdmin) {
+    http_response_code(401);
+    echo json_encode([
+        'ok'    => false,
+        'error' => 'Unauthorized',
+    ]);
+    exit;
+}
+
+// Optional tuning via query params
+$topFolders = isset($_GET['topFolders']) ? max(1, (int)$_GET['topFolders']) : 5;
+$topFiles   = isset($_GET['topFiles'])   ? max(0, (int)$_GET['topFiles'])   : 0;
+
+try {
+    $summary = DiskUsageModel::getSummary($topFolders, $topFiles);
+    http_response_code($summary['ok'] ? 200 : 404);
+    echo json_encode($summary, JSON_UNESCAPED_SLASHES);
+} catch (Throwable $e) {
+    http_response_code(500);
+    echo json_encode([
+        'ok'      => false,
+        'error'   => 'internal_error',
+        'message' => $e->getMessage(),
+    ]);
+}