fix(export): add fileNamingMode support to fix date-range naming mode not working

The 'Date Range' option in Export Global Settings -> File Naming Mode
was not taking effect because fileNamingMode was missing from the
frontend ExportOptions type, default options, config loading, and
the settings-change propagation callback.

- types.ts: add fileNamingMode field to ExportOptions interface
- constants.ts: add fileNamingMode default value
- useExportConfig.ts: load fileNamingMode on init, persist on update
- ExportPage.tsx: propagate fileNamingMode in handleExportDefaultsChanged
  also fix incorrect format key (defaultFormat -> format)

src/pages/Export/ExportPage.tsx

@@ -26,7 +26,7 @@ import { useAutomationRunner, useAutomationStore } from './hooks/useAutomation'
 import { AutomationModal } from './components/Automation/AutomationModal'
 import { AutomationTaskForm } from './components/Automation/AutomationTaskForm'
 
-import type { SessionRow } from './types'
+import type { SessionRow, TextExportFormat } from './types'
 import { getSelectionScopeFromRows, resolveScopeDisplayNames } from './utils/session'
 import {
   emitSingleExportDialogStatus,
@@ -134,8 +134,9 @@ function ExportPage() {
 
   const handleExportDefaultsChanged = useCallback((patch: ExportDefaultsSettingsPatch) => {
     updateOptions({
-      ...(patch.format ? { defaultFormat: patch.format as any } : {}),
+      ...(patch.format ? { format: patch.format as TextExportFormat } : {}),
       ...(patch.avatars !== undefined ? { exportAvatars: patch.avatars } : {}),
+      ...(patch.fileNamingMode !== undefined ? { fileNamingMode: patch.fileNamingMode } : {}),
     })
   }, [updateOptions])
 

src/pages/Export/constants.ts

@@ -175,7 +175,8 @@ export const createDefaultExportOptions = (): import('./types').ExportOptions =>
   excelCompactColumns: true,
   txtColumns: defaultTxtColumns,
   displayNamePreference: 'remark',
-  exportConcurrency: 2
+  exportConcurrency: 2,
+  fileNamingMode: 'classic'
 })
 
 // ─── Empty progress factory ──────────────────────────────────

src/pages/Export/hooks/useExportConfig.ts

@@ -62,7 +62,8 @@ export function useExportConfig(): ExportConfigResult {
           pathStyle,
           excelCompact,
           txtCols,
-          concurrency
+          concurrency,
+          fileNamingMode
         ] = await Promise.all([
           configService.getExportPath(),
           configService.getExportWriteLayout(),
@@ -74,7 +75,8 @@ export function useExportConfig(): ExportConfigResult {
           configService.getExportDefaultPathStyle(),
           configService.getExportDefaultExcelCompactColumns(),
           configService.getExportDefaultTxtColumns(),
-          configService.getExportDefaultConcurrency()
+          configService.getExportDefaultConcurrency(),
+          configService.getExportDefaultFileNamingMode()
         ])
 
         if (!isMounted) return
@@ -118,6 +120,7 @@ export function useExportConfig(): ExportConfigResult {
         if (typeof excelCompact === 'boolean') newOptions.excelCompactColumns = excelCompact
         if (Array.isArray(txtCols)) newOptions.txtColumns = txtCols
         if (typeof concurrency === 'number' && concurrency > 0) newOptions.exportConcurrency = concurrency
+        if (fileNamingMode === 'classic' || fileNamingMode === 'date-range') newOptions.fileNamingMode = fileNamingMode
 
         // Date range
         setRawDateRangeConfigState(dateRange)
@@ -192,6 +195,9 @@ export function useExportConfig(): ExportConfigResult {
       if (patch.exportConcurrency !== undefined) {
         void configService.setExportDefaultConcurrency(patch.exportConcurrency)
       }
+      if (patch.fileNamingMode !== undefined) {
+        void configService.setExportDefaultFileNamingMode(patch.fileNamingMode)
+      }
       
       // Auto-derive exportMedia
       next.exportMedia = (

src/pages/Export/types.ts

@@ -75,6 +75,7 @@ export interface ExportOptions {
   txtColumns: string[]
   displayNamePreference: DisplayNamePreference
   exportConcurrency: number
+  fileNamingMode: 'classic' | 'date-range'
 }
 
 // ─── Session ─────────────────────────────────────────────────