fix: Krea-Bild-URLs auf /api/images/file/ korrigieren, Thumbnail-Endpoint hinzufügen

- ui.js: [Krea: datei] URLs von /api/skills/krea-api/output/ auf /api/images/file/ geändert
- KreaEndpoint: GET /api/images/file/{filename}/thumb mit gecachten WebP-Thumbnails (320px)
- Thumbnail-Cache in data/cache/images/, analog zum SkillEndpoint

Endpoints/KreaEndpoint.cs

@@ -1,3 +1,5 @@
+using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Text.Json;
 using System.Threading.Tasks;
@@ -5,6 +7,9 @@ using Gott.Services;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
+using SixLabors.ImageSharp;
+using SixLabors.ImageSharp.Processing;
+using SixLabors.ImageSharp.Formats.Webp;
 
 namespace Gott.Endpoints
 {
@@ -15,6 +20,7 @@ namespace Gott.Endpoints
             app.MapPost("/api/images/generate", HandleGenerate);
             app.MapGet("/api/images", HandleList);
             app.MapGet("/api/images/file/{filename}", HandleFile);
+            app.MapGet("/api/images/file/{filename}/thumb", HandleThumb);
             app.MapGet("/api/images/status", HandleStatus);
         }
 
@@ -108,5 +114,78 @@ namespace Gott.Endpoints
                 models = KreaService.IMAGE_MODELS.Keys,
             });
         }
+
+        private static readonly HashSet<string> ThumbExtensions = new(StringComparer.OrdinalIgnoreCase)
+        {
+            ".png", ".jpg", ".jpeg", ".gif", ".webp", ".bmp"
+        };
+
+        private static async Task HandleThumb(HttpRequest req, HttpResponse res, KreaService krea, string filename)
+        {
+            if (filename.Contains("..") || filename.Contains("/") || filename.Contains("\\"))
+            {
+                res.StatusCode = 400;
+                return;
+            }
+
+            var ext = Path.GetExtension(filename);
+            if (!ThumbExtensions.Contains(ext))
+            {
+                res.StatusCode = 400;
+                return;
+            }
+
+            var originalPath = krea.GetImagePath(filename);
+            if (originalPath == null)
+            {
+                res.StatusCode = 404;
+                return;
+            }
+
+            // Cache-Verzeichnis: data/cache/images/
+            var imagesDir = Path.GetDirectoryName(originalPath);
+            var dataDir = Path.GetDirectoryName(imagesDir);
+            var cacheDir = Path.Combine(dataDir, "cache", "images");
+            Directory.CreateDirectory(cacheDir);
+
+            var thumbFilename = Path.GetFileNameWithoutExtension(filename) + ".webp";
+            var thumbPath = Path.Combine(cacheDir, thumbFilename);
+
+            if (!File.Exists(thumbPath) || File.GetLastWriteTimeUtc(originalPath) > File.GetLastWriteTimeUtc(thumbPath))
+            {
+                try
+                {
+                    using var image = await Image.LoadAsync(originalPath);
+                    var maxSize = 320;
+                    image.Mutate(x => x.Resize(new ResizeOptions
+                    {
+                        Size = new Size(maxSize, maxSize),
+                        Mode = ResizeMode.Max
+                    }));
+                    var encoder = new WebpEncoder { Quality = 75 };
+                    await image.SaveAsync(thumbPath, encoder);
+                }
+                catch
+                {
+                    // Fallback: Original ausliefern
+                    var contentType = ext switch
+                    {
+                        ".png"  => "image/png",
+                        ".jpg"  => "image/jpeg",
+                        ".jpeg" => "image/jpeg",
+                        ".gif"  => "image/gif",
+                        _       => "image/webp",
+                    };
+                    res.ContentType = contentType;
+                    res.Headers["Cache-Control"] = "private, max-age=3600";
+                    await res.SendFileAsync(originalPath);
+                    return;
+                }
+            }
+
+            res.ContentType = "image/webp";
+            res.Headers["Cache-Control"] = "private, max-age=86400";
+            await res.SendFileAsync(thumbPath);
+        }
     }
 }

wwwroot/js/ui.js

@@ -170,8 +170,8 @@ function renderMarkdown(text) {
   html = html.replace(/\[Krea:\s*([^\]]+)\]/g, function(match, filename) {
     var fn = filename.trim();
     var safeFn = esc(fn);
-    var thumbUrl = '/api/skills/krea-api/output/' + encodeURIComponent(fn) + '/thumb';
-    var fullUrl = '/api/skills/krea-api/output/' + encodeURIComponent(fn);
+    var thumbUrl = '/api/images/file/' + encodeURIComponent(fn) + '/thumb';
+    var fullUrl = '/api/images/file/' + encodeURIComponent(fn);
     return '<span class="krea-ref" data-filename="' + safeFn + '" data-fullurl="' + fullUrl + '" title="Klicken für Vollbild">'
       + '<img class="krea-thumb" src="' + thumbUrl + '" alt="' + safeFn + '" loading="lazy">'
       + '</span>';