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

Models/KreaImageRecord.cs

@@ -0,0 +1,24 @@
+using System.Collections.Generic;
+
+namespace Gott.Models
+{
+    public class KreaImageRecord
+    {
+        public string Id { get; set; }
+        public string Prompt { get; set; }
+        public string Model { get; set; }
+        public int Width { get; set; }
+        public int Height { get; set; }
+        public int Steps { get; set; }
+        public double GuidanceScale { get; set; }
+        public string Seed { get; set; }
+        public int BatchSize { get; set; }
+        public string Status { get; set; } // pending, completed, failed
+        public List<string> Files { get; set; } = new List<string>();
+        public List<string> Urls { get; set; } = new List<string>();
+        public string Error { get; set; }
+        public string CreatedAt { get; set; }
+        public string CompletedAt { get; set; }
+        public string MetaFile { get; set; }
+    }
+}