fix(export): use axiosInstance to ensure correct backend URL and auth

- Changed useExport.ts to import and use axiosInstance from api.ts
- This ensures requests go to port 8918 (backend) not 8919 (frontend)
- Removed manual token handling (axiosInstance interceptor handles it)
- Removed /api prefix from paths (axiosInstance baseURL has the full URL)
- Exported axiosInstance from api.ts for reuse in other modules
- Fixes 404 errors caused by requests routing to frontend instead of backend

frontend/hooks/useExport.ts

@@ -1,5 +1,5 @@
 import { useState } from "react";
-import axios from "axios";
+import { axiosInstance } from "../lib/api";
 
 interface UseExportReturn {
   exportSnapshot: (format: "csv" | "xlsx") => Promise<void>;
@@ -49,12 +49,10 @@ export function useExport(): UseExportReturn {
     setError(null);
 
     try {
-      const token = localStorage.getItem('inventory_token');
-      const response = await axios.get(
-        `/api/admin/db/export?format=${format}&type=inventory`,
+      const response = await axiosInstance.get(
+        `/admin/db/export?format=${format}&type=inventory`,
         {
-          responseType: "blob",
-          headers: { 'Authorization': `Bearer ${token}` }
+          responseType: "blob"
         }
       );
 
@@ -84,12 +82,10 @@ export function useExport(): UseExportReturn {
     setError(null);
 
     try {
-      const token = localStorage.getItem('inventory_token');
-      const response = await axios.get(
-        `/api/admin/db/export?format=${format}&type=audit`,
+      const response = await axiosInstance.get(
+        `/admin/db/export?format=${format}&type=audit`,
         {
-          responseType: "blob",
-          headers: { 'Authorization': `Bearer ${token}` }
+          responseType: "blob"
         }
       );