feat(T08): Bildretusche via Flux.1-Pro + Preisvergleich + Retouch UI with before/after slider

frontend/lib/retouch.ts

@@ -0,0 +1,93 @@
+import { apiFetch, type PaginatedResponse } from './api';
+
+export interface RetouchResultResponse {
+  id: string;
+  vehicle_id?: string | null;
+  original_file_path: string;
+  original_file_name: string;
+  mime_type: string;
+  retouched_file_path?: string | null;
+  status: 'pending' | 'processing' | 'completed' | 'failed';
+  error_message?: string | null;
+  created_at?: string;
+  updated_at?: string;
+}
+
+export interface RetouchProcessResponse {
+  message: string;
+  retouch_id: string;
+  status: string;
+}
+
+export interface ComparableListing {
+  title: string;
+  make: string;
+  model: string;
+  year?: number | null;
+  price: number;
+  mileage_km?: number | null;
+  location?: string | null;
+  url?: string | null;
+  source: string;
+}
+
+export interface PriceCompareResponse {
+  vehicle_id: string;
+  comparable_listings: ComparableListing[];
+  average_price: number | null;
+  listing_count: number;
+}
+
+export async function uploadRetouchImage(
+  file: File,
+  vehicleId?: string
+): Promise<RetouchProcessResponse> {
+  const formData = new FormData();
+  formData.append('file', file);
+  if (vehicleId) {
+    formData.append('vehicle_id', vehicleId);
+  }
+
+  const token = typeof window !== 'undefined' ? localStorage.getItem('access_token') : null;
+  const headers: Record<string, string> = {};
+  if (token) {
+    headers['Authorization'] = `Bearer ${token}`;
+  }
+
+  const API_BASE_URL = process.env.NEXT_PUBLIC_API_URL || 'http://localhost:8000/api/v1';
+  const response = await fetch(`${API_BASE_URL}/retouch/process`, {
+    method: 'POST',
+    headers,
+    body: formData,
+  });
+
+  if (!response.ok) {
+    const err = await response.json().catch(() => ({ error: { code: 'UNKNOWN', message: 'Upload failed' } }));
+    throw err;
+  }
+
+  return response.json();
+}
+
+export async function getRetouchResult(id: string): Promise<RetouchResultResponse> {
+  return apiFetch<RetouchResultResponse>(`/retouch/results/${id}`);
+}
+
+export async function listRetouchResults(
+  vehicleId?: string,
+  page = 1,
+  pageSize = 20
+): Promise<PaginatedResponse<RetouchResultResponse>> {
+  const params = new URLSearchParams();
+  if (vehicleId) params.set('vehicle_id', vehicleId);
+  params.set('page', String(page));
+  params.set('page_size', String(pageSize));
+  return apiFetch<PaginatedResponse<RetouchResultResponse>>(`/retouch/results?${params.toString()}`);
+}
+
+export async function comparePrices(vehicleId: string): Promise<PriceCompareResponse> {
+  return apiFetch<PriceCompareResponse>('/retouch/price-compare', {
+    method: 'POST',
+    body: JSON.stringify({ vehicle_id: vehicleId }),
+  });
+}