feat: add frontend import UI (refs #26)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/features/settings/api/import.api.ts

@@ -0,0 +1,45 @@
+/**
+ * @ai-summary API client for user data import
+ * @ai-context Uploads import archive, generates preview, executes import
+ */
+
+import { apiClient } from '../../../core/api/client';
+import { ImportPreview, ImportResult } from '../types/import.types';
+
+export const importApi = {
+  /**
+   * Generate preview of import data
+   */
+  getPreview: async (file: File): Promise<ImportPreview> => {
+    const formData = new FormData();
+    formData.append('file', file);
+
+    const response = await apiClient.post('/user/import/preview', formData, {
+      headers: {
+        'Content-Type': 'multipart/form-data',
+      },
+      timeout: 120000, // 2 minute timeout for large files
+    });
+    return response.data;
+  },
+
+  /**
+   * Execute import with specified mode
+   */
+  executeImport: async (
+    file: File,
+    mode: 'merge' | 'replace'
+  ): Promise<ImportResult> => {
+    const formData = new FormData();
+    formData.append('file', file);
+    formData.append('mode', mode);
+
+    const response = await apiClient.post('/user/import', formData, {
+      headers: {
+        'Content-Type': 'multipart/form-data',
+      },
+      timeout: 120000, // 2 minute timeout for large imports
+    });
+    return response.data;
+  },
+};