Merge pull request 'Enable de-DE culture with ICU runtime image' (#3) from fix/de-de-culture into main

Reviewed-on: #3

Dockerfile

@@ -1,21 +1,22 @@
 # syntax=docker/dockerfile:1
 
-# --- Build-Stufe: SDK-Image kompiliert und published die App ---
+# --- Build stage: the SDK image compiles and publishes the app ---
 FROM mcr.microsoft.com/dotnet/sdk:10.0 AS build
 WORKDIR /src
 
-# Zuerst nur die csproj kopieren und restoren, damit der NuGet-Restore-Layer
-# gecacht bleibt, solange sich die Abhaengigkeiten nicht aendern.
+# Copy only the csproj and restore first, so the NuGet restore layer stays
+# cached as long as the dependencies do not change.
 COPY Elternbeirat.Web/Elternbeirat.Web.csproj Elternbeirat.Web/
 RUN dotnet restore Elternbeirat.Web/Elternbeirat.Web.csproj
 
-# Dann der restliche Quellcode.
+# Then the rest of the source.
 COPY . .
 RUN dotnet publish Elternbeirat.Web/Elternbeirat.Web.csproj -c Release -o /app
 
-# --- Runtime-Stufe: schlankes chiseled-Image, laeuft als non-root (UID 1654),
-# hoert auf Port 8080, enthaelt keine Shell (kein HEALTHCHECK mit curl/sh). ---
-FROM mcr.microsoft.com/dotnet/aspnet:10.0-noble-chiseled AS runtime
+# --- Runtime stage: slim chiseled image, runs as non-root (UID 1654), listens
+# on port 8080, has no shell (no HEALTHCHECK with curl/sh). The "extra" variant
+# carries ICU and tzdata, which the pages need to format German (de-DE) dates. ---
+FROM mcr.microsoft.com/dotnet/aspnet:10.0-noble-chiseled-extra AS runtime
 WORKDIR /app
 COPY --from=build /app .
 EXPOSE 8080

Elternbeirat.Web/Elternbeirat.Web.csproj

@@ -5,6 +5,10 @@
         <Nullable>enable</Nullable>
         <ImplicitUsings>enable</ImplicitUsings>
         <BlazorDisableThrowNavigationException>true</BlazorDisableThrowNavigationException>
+        <!-- The pages format dates in German (de-DE). Without this the runtime
+             falls back to invariant-only globalization and any named culture
+             throws. Needs an ICU-carrying runtime image (see Dockerfile). -->
+        <InvariantGlobalization>false</InvariantGlobalization>
     </PropertyGroup>
 
     <!-- The test project uses WebApplicationFactory<Program>, which needs the