feat: 电商页面 KeepAlive 保活机制，切换页面不再丢失生成状态

通过 display:none 模式实现轻量 KeepAlive，电商页面首次访问后保持挂载，
切换到其他页面再切回时所有右侧面板状态（上传图片、生成进度、结果）完整保留。
同时清理项目中的临时文件和本地冗余图片。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/features/ecommerce/ecommerceImageValidation.ts

@@ -0,0 +1,37 @@
+export const ECOMMERCE_SUPPORTED_IMAGE_TYPES = new Set(["image/jpeg", "image/png", "image/webp", "image/gif"]);
+export const ECOMMERCE_MAX_IMAGE_BYTES = 10 * 1024 * 1024;
+
+export interface EcommerceImageValidationResult {
+  accepted: File[];
+  rejected: Array<{ name: string; reason: string }>;
+}
+
+export function validateEcommerceImageFiles(files: File[]): EcommerceImageValidationResult {
+  const accepted: File[] = [];
+  const rejected: EcommerceImageValidationResult["rejected"] = [];
+
+  files.forEach((file) => {
+    if (!ECOMMERCE_SUPPORTED_IMAGE_TYPES.has(file.type)) {
+      rejected.push({ name: file.name, reason: "不支持的图片格式" });
+      return;
+    }
+    if (file.size > ECOMMERCE_MAX_IMAGE_BYTES) {
+      rejected.push({ name: file.name, reason: "图片超过 10MB" });
+      return;
+    }
+    accepted.push(file);
+  });
+
+  return { accepted, rejected };
+}
+
+export function summarizeRejectedImages(rejected: EcommerceImageValidationResult["rejected"]): string {
+  if (!rejected.length) return "";
+  const first = rejected[0];
+  const suffix = rejected.length > 1 ? ` 等 ${rejected.length} 个文件` : "";
+  return `${first.name}${suffix} 已跳过：${first.reason}`;
+}
+
+export function normalizeEcommerceImageMime(type: string): string {
+  return ECOMMERCE_SUPPORTED_IMAGE_TYPES.has(type) ? type : "image/png";
+}