refactor(data): consolidate data layer under services namespace

- Move src/data/{api,dto,schemas} directories to src/data/services/*
- Update all relative imports across the codebase to reference new paths
- Use CSS color tokens for splash button gradient in splash-button.module.css
- Add responsive sizes attribute to splash background image
- Add JSDoc documentation to splash-background component referencing original Dart implementation

src/data/services/api/interceptor/logging_interceptor.ts

@@ -0,0 +1,85 @@
+/**
+ * 日志拦截器
+ *
+ * 在开发模式下记录请求/响应/错误日志。
+ * 原始 Dart: lib/core/net/interceptor/app_interceptor.dart 中的日志部分。
+ */
+import type { FetchHook } from "ofetch";
+
+const TAG = "[API]";
+
+function isDev(): boolean {
+  return process.env.NODE_ENV !== "production";
+}
+
+function getRequestUrl(request: Request | string): string {
+  return typeof request === "string" ? request : request.url;
+}
+
+function getRequestMethod(
+  request: Request | string,
+  options: { method?: string }
+): string {
+  return request instanceof Request ? request.method : options.method ?? "GET";
+}
+
+function formatBody(body: unknown): string {
+  if (body === undefined || body === null) return "";
+  try {
+    if (body instanceof FormData) {
+      const entries: string[] = [];
+      body.forEach((value, key) => {
+        if (value instanceof File) {
+          entries.push(`${key}=File(${value.name})`);
+        } else {
+          entries.push(`${key}=${String(value)}`);
+        }
+      });
+      return `FormData{${entries.join(", ")}}`;
+    }
+    return JSON.stringify(body);
+  } catch {
+    return String(body);
+  }
+}
+
+export const onRequestLogging: FetchHook = async (ctx) => {
+  if (!isDev()) return;
+  const method = getRequestMethod(ctx.request, ctx.options);
+  const url = getRequestUrl(ctx.request);
+  console.log(
+    `${TAG} → ${method} ${url}`,
+    ctx.options.body !== undefined ? formatBody(ctx.options.body) : ""
+  );
+};
+
+export const onResponseLogging: FetchHook = async (ctx) => {
+  if (!isDev() || !ctx.response) return;
+  const method = getRequestMethod(ctx.request, ctx.options);
+  const url = getRequestUrl(ctx.request);
+  console.log(
+    `${TAG} ← ${ctx.response.status} ${method} ${url}`,
+    formatBody(ctx.response._data)
+  );
+};
+
+export const onErrorLogging: FetchHook = async (ctx) => {
+  if (!isDev()) return;
+  const status = ctx.response?.status ?? "N/A";
+  const method = getRequestMethod(ctx.request, ctx.options);
+  const url = getRequestUrl(ctx.request);
+  console.error(
+    `${TAG} ✕ ${status} ${method} ${url}`,
+    ctx.error?.message ?? "Unknown error"
+  );
+};
+
+/**
+ * 兼容旧接口的 FetchHooks 形式（保留以备兼容）
+ */
+export const loggingInterceptor = {
+  onRequest: onRequestLogging,
+  onResponse: onResponseLogging,
+  onResponseError: onErrorLogging,
+  onRequestError: onErrorLogging,
+};