fix: login redirect and res.data access in auth/test/sync APIs

- Fix auth.ts: login/getMe now unwrap res.data before returning
- Fix DataSource.vue: testConnection/syncMetadata use res.data.success/message
- Fix Project.vue: autoClassify uses res.data.message
- Root cause: request.ts interceptor returns full response body, auth.ts was
treating response as if it was already unwrapped

frontend/src/views/datasource/DataSource.vue

@@ -207,10 +207,10 @@ function handleEdit(row: DataSourceItem) {
 async function handleTest() {
   try {
     const res: any = await testConnection({ ...form })
-    if (res.success) {
-      ElMessage.success(res.message)
+    if (res.data?.success) {
+      ElMessage.success(res.data?.message)
     } else {
-      ElMessage.error(res.message)
+      ElMessage.error(res.data?.message || '测试失败')
     }
   } catch (e: any) {
     ElMessage.error(e?.message || '测试失败')
@@ -254,10 +254,10 @@ async function handleSync(row: DataSourceItem) {
   try {
     await ElMessageBox.confirm('确认同步该数据源的元数据？', '提示', { type: 'info' })
     const res: any = await syncMetadata(row.id)
-    if (res.success) {
-      ElMessage.success(res.message)
+    if (res.data?.success) {
+      ElMessage.success(res.data?.message)
     } else {
-      ElMessage.error(res.message)
+      ElMessage.error(res.data?.message || '同步失败')
     }
   } catch (e: any) {
     if (e !== 'cancel') ElMessage.error(e?.message || '同步失败')