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/assets/utils/db_auth.php

@@ -20,6 +20,17 @@ if (!function_exists('require_role')) {
     }
 }
 
+// Blocks users whose app_access does not include $app ('all' includes every app).
+if (!function_exists('require_app_access')) {
+    function require_app_access(string $app): void {
+        $access = $_SESSION['login_app_access'] ?? 'wms';
+        if ($access !== 'all' && $access !== $app) {
+            http_response_code(403);
+            exit(json_encode(['success' => 0, 'message' => 'You do not have access to this app.']));
+        }
+    }
+}
+
 if(!empty($_SESSION["login_company_id"])){
 
     // CSRF Validation — add right at the top of the logged-in block