Edit API_URL to dynamic var for deploy

frontend/src/App.js

@@ -1,6 +1,7 @@
 import React, { useEffect, useState, useRef } from "react";
 
 function App() {
+  const API_BASE = process.env.REACT_APP_API_URL || "myday.samuelzielke.de";
   const [datum, setDatum] = useState("2025-05-14");
   const [data, setData] = useState({ abwesenheiten: [], zeitslots: [] });
   const [startzeit, setStartzeit] = useState(null);
@@ -48,8 +49,8 @@ function App() {
   const handleSaveEdit = async (typ) => {
     const url =
       typ === "abwesenheit"
-        ? `http://localhost:3001/api/abwesenheit/${editAbwesenheitId}`
-        : `http://localhost:3001/api/zeitslot/${editZeitslotId}`;
+        ? `${API_BASE}/api/abwesenheit/${editAbwesenheitId}`
+        : `${API_BASE}/api/zeitslot/${editZeitslotId}`;
     await fetch(url, {
       method: "PUT",
       headers: { "Content-Type": "application/json" },
@@ -63,7 +64,7 @@ function App() {
 
   const handleSaveNew = async () => {
     const endpoint = isAbwesenheit ? "abwesenheit" : "zeitslot";
-    await fetch(`http://localhost:3001/api/${endpoint}`, {
+    await fetch(`${API_BASE}/api/${endpoint}`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify({ datum, ...newEntry }),
@@ -74,7 +75,7 @@ function App() {
   };
 
   const deleteEntry = async (id, typ) => {
-    const url = `http://localhost:3001/api/${typ}/${id}`;
+    const url = `${API_BASE}/api/${typ}/${id}`;
     await fetch(url, { method: "DELETE" });
     reloadData();
     if (typ === "abwesenheit") setEditAbwesenheitId(null);
@@ -83,7 +84,7 @@ function App() {
 
   // Daten laden
   useEffect(() => {
-    fetch(`http://localhost:3001/api/data/${datum}`)
+    fetch(`${API_BASE}/api/data/${datum}`)
       .then((res) => res.json())
       .then((data) => {
         setData(data);
@@ -94,7 +95,7 @@ function App() {
 
 
   const reloadData = () => {
-    fetch(`http://localhost:3001/api/data/${datum}`)
+    fetch(`${API_BASE}/api/data/${datum}`)
       .then((res) => res.json())
       .then((data) => {
         setData(data);
@@ -111,7 +112,7 @@ function App() {
   };
 
   const saveManualEndzeit = async () => {
-    await fetch("http://localhost:3001/api/endzeit", {
+    await fetch(`${API_BASE}/api/endzeit`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify({ datum, zeit: manualEndzeit }),
@@ -129,7 +130,7 @@ function App() {
   };
 
   const saveManualStartzeit = async () => {
-    await fetch("http://localhost:3001/api/startzeit", {
+    await fetch(`${API_BASE}/api/startzeit`, {
       method: "POST",
       headers: { "Content-Type": "application/json" },
       body: JSON.stringify({ datum, zeit: manualStartzeit }),