feat: complete export/import cycle and remove sample data

Export now includes invoice_payments and recurring_invoices tables.
Import restored to use ID-based lookups and all fields for clients,
projects, tasks, and time entries. Added missing import support for
timeline_events, calendar_sources, calendar_events, invoice_payments,
and recurring_invoices. Export uses native save dialog instead of blob
download. Removed sample data seeding (seed.rs, UI, command).

src/components/JsonImportWizard.vue

@@ -26,11 +26,20 @@ const entityLabels: Record<string, string> = {
   tasks: 'Tasks',
   time_entries: 'Time Entries',
   tags: 'Tags',
+  entry_tags: 'Entry Tags',
   invoices: 'Invoices',
   invoice_items: 'Invoice Items',
+  invoice_payments: 'Invoice Payments',
+  recurring_invoices: 'Recurring Invoices',
   expenses: 'Expenses',
   favorites: 'Favorites',
   recurring_entries: 'Recurring Entries',
+  tracked_apps: 'Tracked Apps',
+  timeline_events: 'Timeline Events',
+  calendar_sources: 'Calendar Sources',
+  calendar_events: 'Calendar Events',
+  timesheet_locks: 'Timesheet Locks',
+  timesheet_rows: 'Timesheet Rows',
   entry_templates: 'Entry Templates',
   settings: 'Settings',
 }