finally it seems to work

client/.dockerignore

@@ -0,0 +1,3 @@
+.parcel-cache
+dist
+node_modules

client/package.json

@@ -5,10 +5,9 @@
   "author": "Stepan Usatiuk",
   "source": "src/index.html",
   "scripts": {
-    "start": "parcel",
-    "build": "parcel build"
+    "start": "parcel --public-url /app",
+    "build": "parcel build --public-url /app"
   },
-  "publicUrl": "/app",
   "browserslist": "> 0.5%, last 2 versions, not dead",
   "dependencies": {
     "jwt-decode": "^4.0.0",

client/src/api/utils.ts

@@ -10,7 +10,7 @@ declare const process: {
 };
 
 const apiRoot: string =
-    process.env.NODE_ENV == "production" ? "/" : "http://localhost:8080";
+    process.env.NODE_ENV == "production" ? "" : "http://localhost:8080";
 
 let token: string | null;