Complete export/import stub pages

[srgvg]

Context

Several export/import pages are minimal stubs that need to be fleshed out into full detail views with real API data:

Page	Lines	Status
ExportDetailPage.vue	43	Stub
ImportDetailPage.vue	34	Stub
ExportHistoryPage.vue	70	Minimal
ImportHistoryPage.vue	57	Minimal

Work Required

ExportDetailPage.vue (43 lines → full detail view)

• Display export metadata (type, format, timestamp, status)
• Show export contents/preview
• Download action for exported data
• Re-export / delete actions

ImportDetailPage.vue (34 lines → full detail view)

• Display import metadata and status
• Show import results (success/failure per item)
• Rollback action if supported

ExportHistoryPage.vue (70 lines → full list view)

• Paginated export history list
• Filter by type, format, date range
• Bulk actions (delete old exports)

ImportHistoryPage.vue (57 lines → full list view)

• Paginated import history list
• Filter by status, date range
• Import result summary per entry

Affected Files

• ui/src/pages/ExportDetailPage.vue
• ui/src/pages/ImportDetailPage.vue
• ui/src/pages/ExportHistoryPage.vue
• ui/src/pages/ImportHistoryPage.vue
• ui/src/stores/export.ts

Acceptance Criteria

• All four pages display real data from API
• Detail pages show comprehensive information
• History pages support pagination and filtering
• Appropriate actions available on each page
• Loading states and error handling