Link-Fixes: Sprachumschalter, Canonical, og:locale, Legal-Platzhalter, serve-Fallback

- Builder.cs: Sprachumschalter-Links verwenden /{lang}/{slug}.html statt
  /{lang}/{slug}/ (Dateien liegen flach als lang/slug.html)
- Builder.cs: Canonical/OG-URL enthält jetzt /{lang}/-Präfix
- Builder.cs: Legal-Seiten ersetzen {{intro}}, {{positioning}}, {{publisher}}
  mit leerem String (waren zuvor als Artefakte im HTML sichtbar)
- Builder.cs: Sitemap-URLs enthalten Sprach-Präfix + .html
- BuildConfig.cs: JsonNamingPolicy.SnakeCaseLower für korrekte Deserialisierung
  von snake_case JSON-Properties (og_locale → OgLocale, base_url → BaseUrl)
- Program.cs: webstatic serve hat .html-Fallback ( /de/slug → de/slug.html)

src/BuildConfig.cs

@@ -99,7 +99,11 @@ public class BuildConfig
         try
         {
             var json = File.ReadAllText(configPath);
-            var opts = new JsonSerializerOptions { PropertyNameCaseInsensitive = true };
+            var opts = new JsonSerializerOptions
+            {
+                PropertyNameCaseInsensitive = true,
+                PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+            };
             var fromFile = JsonSerializer.Deserialize<BuildConfig>(json, opts);
             if (fromFile != null)
             {

src/Builder.cs

@@ -105,8 +105,10 @@ public static class Builder
                         ? bannerHtml + htmlContent
                         : htmlContent;
 
-                    var canonical = page.Href.StartsWith("/") ? page.Href : $"/{page.Href}";
+                    var slug = page.Href.Trim('/');
-                    if (!canonical.EndsWith("/")) canonical += "/";
+                    var canonical = string.IsNullOrEmpty(slug)
+                        ? $"/{lang}/"
+                        : $"/{lang}/{slug}.html";
 
                     var defaultTitle = cfg.Site.Title.TryGetValue(lang, out var dt) ? dt : cfg.Site.Name;
                     var defaultDesc = cfg.Site.Description.TryGetValue(lang, out var dd) ? dd : "";
@@ -157,8 +159,8 @@ public static class Builder
                     var ldir = Path.Combine(Directories.DistDir, lang);
                     Directory.CreateDirectory(ldir);
 
-                    var slug = page.Href.Trim('/');
+                    var fileSlug = page.Href.Trim('/');
-                    var outputFile = string.IsNullOrEmpty(slug) ? "index.html" : $"{slug}.html";
+                    var outputFile = string.IsNullOrEmpty(fileSlug) ? "index.html" : $"{fileSlug}.html";
                     var outputPath = Path.Combine(ldir, outputFile);
                     File.WriteAllText(outputPath, pageHtml);
 
@@ -248,7 +250,7 @@ public static class Builder
             var code = (li.HrefLang ?? lang).ToUpperInvariant();
             string slug = "";
             if (langSlug != null && langSlug.TryGetValue(lang, out var h)) slug = h.Trim('/');
-            var href = string.IsNullOrEmpty(slug) ? $"/{lang}/" : $"/{lang}/{slug}/";
+            var href = string.IsNullOrEmpty(slug) ? $"/{lang}/" : $"/{lang}/{slug}.html";
             sb.AppendLine($"          <li><a href=\"{href}\" hreflang=\"{li.HrefLang ?? lang}\"><span>{HtmlEncode(label)}</span> <span class=\"lang-dropdown__code\">{code}</span></a></li>");
         }
         return sb.ToString().Trim();
@@ -403,14 +405,15 @@ public static class Builder
                     htmlContent = MarkdownProcessor.TablePostprocess(htmlContent);
 
                     var baseName = Regex.Replace(bn, @"\.(de|en|vi)\.md$", ".html").Replace(".md", ".html");
-                    var canonical = $"/{Path.GetFileNameWithoutExtension(baseName)}/";
+                    var legalFileName = Path.GetFileNameWithoutExtension(baseName);
+                    var canonical = $"/{lang}/{legalFileName}.html";
                     var defaultTitle = cfg.Site.Title.TryGetValue(lang, out var dt) ? dt : cfg.Site.Name;
                     var defaultDesc = cfg.Site.Description.TryGetValue(lang, out var dd) ? dd : "";
                     var seoHead = SeoHelper.RenderSeoHead(lang, title, "", $"{env.BaseUrl}{canonical}",
                         env.Cdn, defaultTitle, defaultDesc);
                     var sidebarTocHtml = BuildSidebarTocHtml(content);
-                    var legalSlug = $"/{Path.GetFileNameWithoutExtension(baseName)}/";
+                    var legalSlug = $"{legalFileName}.html";
-                    var legalLangSlug = cfg.LanguageCodes().ToDictionary(l => l, l => legalSlug);
+                    var legalLangSlug = cfg.LanguageCodes().ToDictionary(l => l, l => $"{l}/{legalFileName}.html");
                     var langLinksHtml = BuildLangLinksHtml(legalLangSlug);
 
                     var pageHtml = layout
@@ -425,6 +428,9 @@ public static class Builder
                         .Replace("{{lang_links}}", langLinksHtml).Replace("{{ lang_links }}", langLinksHtml)
                         .Replace("{{glossary_href}}", GlossaryHref(lang)).Replace("{{ glossary_href }}", GlossaryHref(lang))
                         .Replace("{{glossary_label}}", GlossaryLabel(lang)).Replace("{{ glossary_label }}", GlossaryLabel(lang))
+                        .Replace("{{intro}}", "").Replace("{{ intro }}", "")
+                        .Replace("{{positioning}}", "").Replace("{{ positioning }}", "")
+                        .Replace("{{publisher}}", "").Replace("{{ publisher }}", "")
                         .Replace("{{content}}", htmlContent).Replace("{{ content }}", htmlContent)
                         .Replace("{{body}}", htmlContent).Replace("{{ body }}", htmlContent);
                     pageHtml = I18n.Substitute(pageHtml, lang);
@@ -452,7 +458,12 @@ public static class Builder
             urls.Add($"{baseUrl}/{lang}/");
             var contents = ContentLoader.LoadContent(Directories.ContentDir, lang);
             foreach (var page in contents)
-                if (page.Meta.Render) urls.Add($"{baseUrl}{page.Href}");
+            {
+                if (!page.Meta.Render) continue;
+                var slug = page.Href.Trim('/');
+                if (!string.IsNullOrEmpty(slug))
+                    urls.Add($"{baseUrl}/{lang}/{slug}.html");
+            }
         }
         var sitemap = @"<?xml version=""1.0"" encoding=""UTF-8""?>
 <urlset xmlns=""http://www.sitemaps.org/schemas/sitemap/0.9"">

src/Program.cs

@@ -339,8 +339,15 @@ static async Task ServeAsync(string distDir, int port)
                 var file = Path.Combine(distDir, reqPath.TrimStart('/'));
                 if (!File.Exists(file))
                 {
-                    file = Path.Combine(distDir, reqPath.TrimStart('/') + "/index.html");
+                    // Try appending .html (e.g. /de/slug → de/slug.html)
-                    if (!File.Exists(file)) file = Path.Combine(distDir, "404.html");
+                    var htmlFile = file.TrimEnd('/') + ".html";
+                    if (File.Exists(htmlFile))
+                        file = htmlFile;
+                    else
+                    {
+                        file = Path.Combine(distDir, reqPath.TrimStart('/') + "/index.html");
+                        if (!File.Exists(file)) file = Path.Combine(distDir, "404.html");
+                    }
                 }
                 if (File.Exists(file))
                 {