Datumsformat konfigurierbar (Einstellungen -> Darstellung)

MHD wurde in den Ansichten noch roh als YYYY-MM-DD ausgegeben. Jetzt:
- Neue Einstellung date_format (23.12.2026 | 23.12.26 | 23. Dezember 2026 |
  2026-12-23 | 12/23/2026) mit Live-Beispiel auf der Einstellungsseite.
- SettingsProvider stellt Format und formatDate() app-weit bereit und laedt die
  Einstellungen nach dem Login.
- Verwendet in Uebersicht (bald ablaufend), Produktdetail (Chargen) und
  Auslagern (Chargenauswahl). Datumsfelder zur Eingabe bleiben ISO, wie es das
  HTML-Datumsfeld verlangt.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/main.jsx

@@ -3,13 +3,16 @@ import ReactDOM from "react-dom/client";
 import { BrowserRouter } from "react-router-dom";
 import App from "./App";
 import { AuthProvider } from "./auth";
+import { SettingsProvider } from "./settings";
 import "./styles.css";
 
 ReactDOM.createRoot(document.getElementById("root")).render(
   <React.StrictMode>
     <BrowserRouter>
       <AuthProvider>
-        <App />
+        <SettingsProvider>
+          <App />
+        </SettingsProvider>
       </AuthProvider>
     </BrowserRouter>
   </React.StrictMode>

web/src/pages/CheckOut.jsx

@@ -1,9 +1,11 @@
 import { useEffect, useState } from "react";
 import { api } from "../api";
 import Icon from "../components/Icon";
+import { useSettings } from "../settings";
 import { buildUnitOptions, fmt, isExpired, unitShort } from "../units";
 
 export default function CheckOut() {
+  const { formatDate } = useSettings();
   const [barcode, setBarcode] = useState("");
   const [search, setSearch] = useState("");
   const [results, setResults] = useState([]);
@@ -159,7 +161,7 @@ export default function CheckOut() {
               <option value="">Automatisch – zuerst ablaufende zuerst (FEFO)</option>
               {lots.map((l) => (
                 <option key={l.id} value={l.id}>
-                  {l.best_before ? `MHD ${l.best_before}` : "ohne MHD"} · {lotAmount(l.quantity)}
+                  {l.best_before ? `MHD ${formatDate(l.best_before)}` : "ohne MHD"} · {lotAmount(l.quantity)}
                   {isExpired(l.best_before) ? " · abgelaufen" : ""}
                 </option>
               ))}
@@ -170,7 +172,7 @@ export default function CheckOut() {
             <div className={`alert ${isExpired(selectedLot.best_before) ? "error" : "info"}`}>
               <Icon name="alert" size={16} />
               Gewählte Charge: {lotAmount(selectedLot.quantity)}
-              {selectedLot.best_before ? ` · MHD ${selectedLot.best_before}` : " · ohne MHD"}
+              {selectedLot.best_before ? ` · MHD ${formatDate(selectedLot.best_before)}` : " · ohne MHD"}
               {isExpired(selectedLot.best_before) ? " (abgelaufen)" : ""}
             </div>
           )}

web/src/pages/Dashboard.jsx

@@ -2,9 +2,11 @@ import { useEffect, useState } from "react";
 import { Link } from "react-router-dom";
 import { api } from "../api";
 import Icon from "../components/Icon";
+import { useSettings } from "../settings";
 import { amountText, articlePrimary, articleSecondary, fmt, relativeExpiry } from "../units";
 
 export default function Dashboard() {
+  const { formatDate } = useSettings();
   const [expiring, setExpiring] = useState([]);
   const [shopping, setShopping] = useState([]);
   const [groupShopping, setGroupShopping] = useState([]);
@@ -89,7 +91,7 @@ export default function Dashboard() {
                           <div className="muted small">{articleSecondary(it)}</div>
                         )}
                       </td>
-                      <td>{it.best_before}</td>
+                      <td>{formatDate(it.best_before)}</td>
                       <td>
                         <span className={`badge ${it.days_left < 0 ? "danger" : "warn"}`}>
                           {relativeExpiry(it.days_left)}

web/src/pages/ProductForm.jsx

@@ -5,6 +5,7 @@ import { useAuth } from "../auth";
 import BarcodeList from "../components/BarcodeList";
 import Icon from "../components/Icon";
 import { guessGroup } from "../offUtils";
+import { useSettings } from "../settings";
 import { daysUntil, expiryRowClass, fmt, isExpired, relativeExpiry, unitShort } from "../units";
 
 const EMPTY = {
@@ -377,6 +378,7 @@ export default function ProductForm() {
 
 /** Chargen-Karte mit Bearbeiten/Löschen. Bearbeitet wird in der Produkteinheit. */
 function LotsCard({ product, lots, baseShort, warnDays, isAdmin, imageUrl, onChanged, onError }) {
+  const { formatDate } = useSettings();
   const [editId, setEditId] = useState(null);
   const [draft, setDraft] = useState({ quantity: "", best_before: "" });
   // In welcher Einheit die Menge bearbeitet wird: "unit" oder "package".
@@ -501,7 +503,7 @@ function LotsCard({ product, lots, baseShort, warnDays, isAdmin, imageUrl, onCha
                         style={{ marginTop: 0, minWidth: 150 }} />
                     ) : (
                       <>
-                        {l.best_before || "–"}
+                        {l.best_before ? formatDate(l.best_before) : "–"}
                         {cls && (
                           <span className={`badge ${cls === "row-danger" ? "danger" : "warn"}`}
                             style={{ marginLeft: 6 }}>

web/src/pages/Settings.jsx

@@ -1,11 +1,15 @@
 import { useEffect, useState } from "react";
 import { api } from "../api";
 import Icon from "../components/Icon";
+import { DATE_FORMAT_KEY, useSettings } from "../settings";
+import { DATE_FORMATS, formatDate } from "../units";
 
 const EXPIRY_KEY = "expiry_warning_days";
 
 export default function Settings() {
+  const { reload } = useSettings();
   const [days, setDays] = useState("");
+  const [dateFormat, setDateFormat] = useState("de");
   const [error, setError] = useState(null);
   const [info, setInfo] = useState(null);
   const [busy, setBusy] = useState(false);
@@ -13,8 +17,8 @@ export default function Settings() {
   async function load() {
     try {
       const settings = await api.listSettings();
-      const row = settings.find((s) => s.key === EXPIRY_KEY);
-      setDays(row ? row.value : "7");
+      setDays(settings.find((s) => s.key === EXPIRY_KEY)?.value ?? "7");
+      setDateFormat(settings.find((s) => s.key === DATE_FORMAT_KEY)?.value ?? "de");
     } catch (err) {
       setError(err.message);
     }
@@ -27,6 +31,8 @@ export default function Settings() {
     setError(null); setInfo(null); setBusy(true);
     try {
       await api.setSetting(EXPIRY_KEY, String(parseInt(days, 10)));
+      await api.setSetting(DATE_FORMAT_KEY, dateFormat);
+      await reload();
       setInfo("Gespeichert.");
     } catch (err) {
       setError(err.message);
@@ -35,6 +41,9 @@ export default function Settings() {
     }
   }
 
+  // Beispiel mit einem festen Datum, damit man die Wirkung sofort sieht.
+  const preview = formatDate("2026-12-23", dateFormat);
+
   return (
     <div>
       <div className="page-head">
@@ -57,6 +66,20 @@ export default function Settings() {
           Chargen, deren Mindesthaltbarkeitsdatum innerhalb dieser Frist liegt (oder
           bereits überschritten ist), erscheinen auf der Übersicht unter „Bald ablaufend".
         </p>
+
+        <div className="card-head" style={{ marginTop: "var(--sp-5)" }}>
+          <Icon name="settings" /><h2>Darstellung</h2>
+        </div>
+        <label>
+          Datumsformat
+          <select value={dateFormat} onChange={(e) => setDateFormat(e.target.value)}>
+            {DATE_FORMATS.map((f) => (
+              <option key={f.value} value={f.value}>{f.label}</option>
+            ))}
+          </select>
+        </label>
+        <p className="muted small mt-0">Beispiel: {preview}</p>
+
         <button className="btn primary" disabled={busy}>{busy ? "Speichern…" : "Speichern"}</button>
       </form>
     </div>

web/src/settings.jsx

@@ -0,0 +1,45 @@
+import { createContext, useCallback, useContext, useEffect, useState } from "react";
+import { api } from "./api";
+import { useAuth } from "./auth";
+import { formatDate } from "./units";
+
+export const DATE_FORMAT_KEY = "date_format";
+const DEFAULT_FORMAT = "de";
+
+const SettingsContext = createContext({
+  dateFormat: DEFAULT_FORMAT,
+  formatDate: (iso) => formatDate(iso, DEFAULT_FORMAT),
+  reload: () => {},
+});
+
+/** Lädt die anzeigerelevanten Einstellungen einmal nach dem Login. */
+export function SettingsProvider({ children }) {
+  const { user } = useAuth();
+  const [dateFormat, setDateFormat] = useState(DEFAULT_FORMAT);
+
+  const reload = useCallback(async () => {
+    try {
+      const rows = await api.listSettings();
+      const row = rows.find((r) => r.key === DATE_FORMAT_KEY);
+      setDateFormat(row?.value || DEFAULT_FORMAT);
+    } catch {
+      /* Einstellungen sind optional – Standard bleibt bestehen. */
+    }
+  }, []);
+
+  useEffect(() => {
+    if (user) reload();
+  }, [user, reload]);
+
+  const value = {
+    dateFormat,
+    formatDate: (iso) => formatDate(iso, dateFormat),
+    reload,
+  };
+
+  return <SettingsContext.Provider value={value}>{children}</SettingsContext.Provider>;
+}
+
+export function useSettings() {
+  return useContext(SettingsContext);
+}

web/src/units.js

@@ -53,6 +53,34 @@ export function isExpired(dateStr) {
   return d != null && d < 0;
 }
 
+// Auswählbare Datumsformate (Einstellungen -> Darstellung).
+export const DATE_FORMATS = [
+  { value: "de", label: "23.12.2026" },
+  { value: "de-short", label: "23.12.26" },
+  { value: "long", label: "23. Dezember 2026" },
+  { value: "iso", label: "2026-12-23" },
+  { value: "us", label: "12/23/2026" },
+];
+
+// Formatiert ein ISO-Datum (YYYY-MM-DD) nach dem gewählten Format.
+export function formatDate(iso, format = "de") {
+  if (!iso) return "–";
+  const date = new Date(`${iso}T00:00:00`);
+  if (Number.isNaN(date.getTime())) return iso;
+  switch (format) {
+    case "iso":
+      return iso;
+    case "de-short":
+      return date.toLocaleDateString("de-DE", { day: "2-digit", month: "2-digit", year: "2-digit" });
+    case "long":
+      return date.toLocaleDateString("de-DE", { day: "numeric", month: "long", year: "numeric" });
+    case "us":
+      return date.toLocaleDateString("en-US");
+    default:
+      return date.toLocaleDateString("de-DE");
+  }
+}
+
 // MHD lesbar als Zeitspanne: "in 3 Tagen", "in 1 Woche", "vor 2 Wochen".
 // Deutsch nach "in"/"vor" steht im Dativ: 1 Tag / 3 Tagen, 1 Woche / 2 Wochen.
 export function relativeExpiry(daysLeft) {