feat: Krea Image Generation Endpoint

- KreaService: GenerateAsync() mit Job-Polling, Image-Download, Metadaten-Speicherung
- KreaEndpoint: POST /api/images/generate, GET /api/images, GET /api/images/file/{filename}, GET /api/images/status
- KreaImageRecord: Output-Model
- Output: data/images/<timestamp>-<index>.<ext> + data/images/<timestamp>.json
- 16 Modelle: flux, flux-kontext, flux-1.1-pro, imagen-3/4, chatgpt-image, runway-gen-4, etc.
- appsettings.json: KreaToken (Format: KEY_ID:SECRET), obsolete TelegramBotToken/WebhookSecret entfernt

Endpoints/KreaEndpoint.cs

@@ -0,0 +1,112 @@
+using System.IO;
+using System.Text.Json;
+using System.Threading.Tasks;
+using Gott.Services;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Routing;
+
+namespace Gott.Endpoints
+{
+    public static class KreaEndpoint
+    {
+        public static void MapKreaEndpoints(this IEndpointRouteBuilder app)
+        {
+            app.MapPost("/api/images/generate", HandleGenerate);
+            app.MapGet("/api/images", HandleList);
+            app.MapGet("/api/images/file/{filename}", HandleFile);
+            app.MapGet("/api/images/status", HandleStatus);
+        }
+
+        private static async Task HandleGenerate(HttpRequest req, HttpResponse res, KreaService krea)
+        {
+            if (!krea.IsConfigured)
+            {
+                res.StatusCode = 400;
+                await res.WriteAsJsonAsync(new { error = "Krea API nicht konfiguriert (KreaToken fehlt)" });
+                return;
+            }
+
+            JsonElement body;
+            try { body = await JsonSerializer.DeserializeAsync<JsonElement>(req.Body); }
+            catch
+            {
+                res.StatusCode = 400;
+                await res.WriteAsJsonAsync(new { error = "Ungültiger JSON-Body" });
+                return;
+            }
+
+            var prompt = body.TryGetProperty("prompt", out var p) ? p.GetString() : null;
+            if (string.IsNullOrWhiteSpace(prompt))
+            {
+                res.StatusCode = 400;
+                await res.WriteAsJsonAsync(new { error = "prompt ist erforderlich" });
+                return;
+            }
+
+            var model         = body.TryGetProperty("model",         out var m)  ? m.GetString()  : "flux";
+            var width         = body.TryGetProperty("width",         out var w)  ? w.GetInt32()   : 1024;
+            var height        = body.TryGetProperty("height",        out var h)  ? h.GetInt32()   : 1024;
+            var steps         = body.TryGetProperty("steps",         out var st) ? st.GetInt32()  : 25;
+            var guidanceScale = body.TryGetProperty("guidanceScale", out var g)  ? g.GetDouble()  : 3.0;
+            var seed          = body.TryGetProperty("seed",          out var sd) ? sd.GetString() : null;
+            var batchSize     = body.TryGetProperty("batchSize",     out var b)  ? b.GetInt32()   : 1;
+
+            try
+            {
+                var result = await krea.GenerateAsync(prompt, model, width, height, steps, guidanceScale, seed, batchSize);
+                await res.WriteAsJsonAsync(result);
+            }
+            catch (System.Exception ex)
+            {
+                res.StatusCode = 500;
+                await res.WriteAsJsonAsync(new { error = ex.Message });
+            }
+        }
+
+        private static async Task HandleList(HttpRequest req, HttpResponse res, KreaService krea)
+        {
+            var images = krea.ListImages();
+            await res.WriteAsJsonAsync(images);
+        }
+
+        private static async Task HandleFile(HttpRequest req, HttpResponse res, KreaService krea, string filename)
+        {
+            // Sicherheitscheck – kein Path Traversal
+            if (filename.Contains("..") || filename.Contains("/") || filename.Contains("\\"))
+            {
+                res.StatusCode = 400;
+                return;
+            }
+
+            var path = krea.GetImagePath(filename);
+            if (path == null)
+            {
+                res.StatusCode = 404;
+                return;
+            }
+
+            var ext = Path.GetExtension(filename).ToLower();
+            var contentType = ext switch
+            {
+                ".png"  => "image/png",
+                ".jpg"  => "image/jpeg",
+                ".jpeg" => "image/jpeg",
+                ".gif"  => "image/gif",
+                _       => "image/webp",
+            };
+
+            res.ContentType = contentType;
+            await res.SendFileAsync(path);
+        }
+
+        private static async Task HandleStatus(HttpRequest req, HttpResponse res, KreaService krea)
+        {
+            await res.WriteAsJsonAsync(new
+            {
+                configured = krea.IsConfigured,
+                models = KreaService.IMAGE_MODELS.Keys,
+            });
+        }
+    }
+}