changed locales from .ts to .json,

configured i18n-ally,
upgrade APIlite and regenerated BackendAPI.ts,
fixed successMessage value

frontend/.vscode/extensions.json

@@ -0,0 +1,9 @@
+{
+  "recommendations": [
+    "Vue.volar",
+    "dbaeumer.vscode-eslint",
+    "EditorConfig.EditorConfig",
+    "oxc.oxc-vscode",
+    "esbenp.prettier-vscode"
+  ]
+}