refactor: 数据处理向导拆分组合式函数与子面板

提取 useDataProcessDraft、useDataProcessGeneration 与 dataProcessCreateState 管理向导状态，新增 StructuredOptionsPanel、UnstructuredOptionsPanel、DatasetSplitEditor 子面板组件，样式抽离为独立 scss，DataProcessCreateView 与 TaskSetupStep 大幅瘦身，回归脚本适配。

frontend/src/views/data-process/create/SourceUploadStep.vue

@@ -1,18 +1,11 @@
 <script setup lang="ts">
 import { computed, ref, watch } from 'vue'
 import type { UploadFile } from 'element-plus'
-import type { ExternalDataSource, ProcessType } from './types'
-
-interface UploadedSourceFile {
-  uid: string | number
-  name: string
-  size: number
-  count: number
-}
+import type { ExternalDataSource, ProcessType, UploadedDataFile } from './types'
 
 const props = defineProps<{
   processType: ProcessType
-  uploadedFiles: UploadedSourceFile[]
+  uploadedFiles: UploadedDataFile[]
   externalSource: ExternalDataSource
   externalPulling: boolean
   externalConnected: boolean