Add Asset Management app

Assets from purchase invoice lines, straight-line depreciation/amortization with salvage value, disposals, and [Asset Mgmt] sources in Batch GL Entries. Green third workspace with an app access guard.

app/asset/api/engine/category.php

@@ -0,0 +1,11 @@
+<?php
+session_start();
+require_once '../../../assets/utils/db_auth.php';
+require_app_access('asset');
+require_once '../../../assets/utils/classes_as/AssetCategoryManager.php';
+
+$categories = new AssetCategoryManager($pdo2, $company_id);
+$answer['output']  = $categories->getAll();
+$answer['stats']   = $categories->getStats();
+$answer['success'] = 1;
+exit(json_encode($answer));