feat: 瀑布流布局

Co-authored-by: Copilot <copilot@github.com>

server/api/images/presets.get.ts

@@ -0,0 +1,75 @@
+// server/api/images/presets.get.ts - 预设提示词列表接口：分页返回已启用的生图预设。
+import type { IPromptPresetListData } from "#shared/types/openai";
+import {
+  createApiLogger,
+  createSuccessResponse,
+  createUpstreamErrorResponse,
+  listPromptPresets,
+  toSafeLogError
+} from "~~/server/utils";
+
+const DEFAULT_PAGE = 1;
+const DEFAULT_PAGE_SIZE = 20;
+const MAX_PAGE_SIZE = 50;
+
+/**
+ * GET /api/images/presets
+ *
+ * 流程：
+ * 1. 读取 page/size 查询参数，并限制最大 pageSize。
+ * 2. 只返回已启用的预设提示词，按导入顺序展示。
+ * 3. 返回前端展示和填充输入所需字段，不包含内部排查信息。
+ */
+export default defineEventHandler(async (event) => {
+  const logger = createApiLogger("images.presets.list");
+  logger.info("开始");
+
+  try {
+    const query = getQuery(event);
+    const page = normalizePositiveInt(query.page, DEFAULT_PAGE);
+    const pageSize = Math.min(
+      normalizePositiveInt(query.size, DEFAULT_PAGE_SIZE),
+      MAX_PAGE_SIZE
+    );
+
+    logger.info("查询参数", {
+      page,
+      pageSize
+    });
+
+    const result = await listPromptPresets({
+      page,
+      pageSize
+    });
+
+    logger.done("成功", {
+      page,
+      pageSize,
+      total: result.total,
+      itemCount: result.items.length
+    });
+
+    return createSuccessResponse<IPromptPresetListData>(
+      result,
+      "获取预设提示词成功"
+    );
+  } catch (error) {
+    logger.error("失败", {
+      error: toSafeLogError(error)
+    });
+    return createUpstreamErrorResponse(error, "获取预设提示词失败");
+  }
+});
+
+/** 将 query 参数归一化为正整数，非法值回退到默认值 */
+const normalizePositiveInt = (
+  value: unknown,
+  fallbackValue: number
+): number => {
+  const rawValue = Array.isArray(value) ? value[0] : value;
+  const numberValue = Number.parseInt(String(rawValue ?? ""), 10);
+
+  return Number.isInteger(numberValue) && numberValue > 0
+    ? numberValue
+    : fallbackValue;
+};