Restructure into feature folders with code-behind and scoped CSS

Elternbeirat.Web/Features/Posts/Post.cs

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+namespace Elternbeirat.Web.Services;
+
+/// <summary>
+/// A news post, read from a Markdown file in <c>Content/posts/</c>. Unlike a
+/// <see cref="Page"/>, a post has a date and
+/// is shown in a chronological list. The file name (without extension) is the
+/// slug.
+/// </summary>
+public sealed class Post
+{
+    /// <summary>
+    /// URL identifier of the post, taken from the file name without umlauts.
+    /// It appears in the route <c>/beitraege/{slug}</c>.
+    /// </summary>
+    public required string Slug { get; init; }
+
+    /// <summary>
+    /// Display title from the YAML front matter (<c>titel:</c>). Falls back to
+    /// the slug when no title is set.
+    /// </summary>
+    public required string Title { get; init; }
+
+    /// <summary>
+    /// Publication date from the front matter (<c>datum:</c>). Used to sort the
+    /// list newest first.
+    /// </summary>
+    public required DateOnly Date { get; init; }
+
+    /// <summary>
+    /// The post body rendered from Markdown to HTML (front matter excluded).
+    /// </summary>
+    public required string ContentHtml { get; init; }
+}

Elternbeirat.Web/Features/Posts/PostDetail.razor

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+@page "/beitraege/{Slug}"
+@inject PostService PostService
+
+@if (_post is null)
+{
+    <PageTitle>Nicht gefunden</PageTitle>
+}
+else
+{
+    <PageTitle>@_post.Title</PageTitle>
+    <article>
+        <p class="post-meta">
+            <a href="/beitraege">&larr; Alle Beiträge</a>
+            <time datetime="@_post.Date.ToString("yyyy-MM-dd")">
+                @_post.Date.ToString("d. MMMM yyyy", German)
+            </time>
+        </p>
+        @((MarkupString)_post.ContentHtml)
+    </article>
+}

Elternbeirat.Web/Features/Posts/PostDetail.razor.cs

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+using System.Globalization;
+using Elternbeirat.Web.Services;
+using Microsoft.AspNetCore.Components;
+using Microsoft.AspNetCore.Http;
+
+namespace Elternbeirat.Web.Features.Posts;
+
+public partial class PostDetail
+{
+    private static readonly CultureInfo German = CultureInfo.GetCultureInfo("de-DE");
+
+    [Parameter]
+    public string Slug { get; set; } = "";
+
+    private Post? _post;
+
+    protected override void OnParametersSet()
+    {
+        _post = PostService.Find(Slug);
+
+        // Unknown slug -> 404, so UseStatusCodePagesWithReExecute serves the
+        // /not-found page instead of an empty 200 response.
+        if (_post is null && HttpContext is not null)
+        {
+            HttpContext.Response.StatusCode = StatusCodes.Status404NotFound;
+        }
+    }
+
+    [CascadingParameter]
+    private HttpContext? HttpContext { get; set; }
+}

Elternbeirat.Web/Features/Posts/PostDetail.razor.css

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+.post-meta {
+    display: flex;
+    justify-content: space-between;
+    align-items: baseline;
+    gap: 1rem;
+    margin-bottom: 1rem;
+}
+
+.post-meta time {
+    display: block;
+    color: #777;
+    font-size: 0.85rem;
+}

Elternbeirat.Web/Features/Posts/PostList.razor

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+@page "/beitraege"
+@inject PostService PostService
+
+<PageTitle>Beiträge</PageTitle>
+
+<h1>Beiträge</h1>
+
+@if (PostService.All.Count == 0)
+{
+    <p>Zurzeit gibt es keine Beiträge.</p>
+}
+else
+{
+    <ul class="post-list">
+        @foreach (var post in PostService.All)
+        {
+            <li>
+                <a href="@($"/beitraege/{post.Slug}")">@post.Title</a>
+                <time datetime="@post.Date.ToString("yyyy-MM-dd")">
+                    @post.Date.ToString("d. MMMM yyyy", German)
+                </time>
+            </li>
+        }
+    </ul>
+}

Elternbeirat.Web/Features/Posts/PostList.razor.cs

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+using System.Globalization;
+
+namespace Elternbeirat.Web.Features.Posts;
+
+public partial class PostList
+{
+    private static readonly CultureInfo German = CultureInfo.GetCultureInfo("de-DE");
+}

Elternbeirat.Web/Features/Posts/PostList.razor.css

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+.post-list {
+    list-style: none;
+    padding: 0;
+}
+
+.post-list li {
+    padding: 0.75rem 0;
+    border-bottom: 1px solid #eee;
+}
+
+.post-list a {
+    font-size: 1.1rem;
+    text-decoration: none;
+}
+
+.post-list time {
+    display: block;
+    color: #777;
+    font-size: 0.85rem;
+}

Elternbeirat.Web/Features/Posts/PostService.cs

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+using System.Globalization;
+using Markdig;
+
+namespace Elternbeirat.Web.Services;
+
+/// <summary>
+/// Reads the news posts from <c>Content/posts/*.md</c>, renders them to HTML
+/// once at startup and keeps them in memory, sorted newest first. Registered as
+/// a singleton because the content lives in the image and does not change at
+/// runtime.
+/// </summary>
+public sealed class PostService
+{
+    private readonly IReadOnlyList<Post> _posts;
+    private readonly IReadOnlyDictionary<string, Post> _postsBySlug;
+
+    /// <summary>
+    /// Reads every Markdown post from the <c>Content/posts</c> directory
+    /// below the application root and caches it.
+    /// </summary>
+    public PostService(IWebHostEnvironment environment)
+    {
+        var pipeline = new MarkdownPipelineBuilder()
+            .UseYamlFrontMatter()
+            .Build();
+
+        var directory = Path.Combine(environment.ContentRootPath, "Content", "posts");
+        var posts = new List<Post>();
+
+        if (Directory.Exists(directory))
+        {
+            foreach (var path in Directory.EnumerateFiles(directory, "*.md"))
+            {
+                posts.Add(Read(path, pipeline));
+            }
+        }
+
+        // Newest first for the list; a stable slug order breaks date ties.
+        posts.Sort((a, b) =>
+        {
+            var byDate = b.Date.CompareTo(a.Date);
+            return byDate != 0 ? byDate : string.CompareOrdinal(a.Slug, b.Slug);
+        });
+
+        _posts = posts;
+        _postsBySlug = posts.ToDictionary(p => p.Slug, StringComparer.OrdinalIgnoreCase);
+    }
+
+    /// <summary>
+    /// All posts, newest first. Used for the overview list.
+    /// </summary>
+    public IReadOnlyList<Post> All => _posts;
+
+    /// <summary>
+    /// Returns the post for the given slug, or <c>null</c> if there is none.
+    /// The lookup is case-insensitive.
+    /// </summary>
+    public Post? Find(string slug) =>
+        _postsBySlug.GetValueOrDefault(slug);
+
+    private static Post Read(string path, MarkdownPipeline pipeline)
+    {
+        var slug = Path.GetFileNameWithoutExtension(path);
+        var source = File.ReadAllText(path);
+
+        var document = Markdown.Parse(source, pipeline);
+        var title = FrontMatter.Read("title", document, source) ?? slug;
+        var date = ParseDate(FrontMatter.Read("date", document, source));
+        var html = Markdown.ToHtml(source, pipeline);
+
+        return new Post { Slug = slug, Title = title, Date = date, ContentHtml = html };
+    }
+
+    /// <summary>
+    /// Parses the <c>datum:</c> value as an ISO date (yyyy-MM-dd). Falls back to
+    /// <see cref="DateOnly.MinValue"/> when the value is missing or malformed,
+    /// so a single bad file does not crash startup — it just sorts last.
+    /// </summary>
+    private static DateOnly ParseDate(string? value)
+    {
+        return DateOnly.TryParse(value, CultureInfo.InvariantCulture,
+            DateTimeStyles.None, out var date)
+            ? date
+            : DateOnly.MinValue;
+    }
+}