feat(import/export): article import + register export (xlsx/csv) (#750)

* feat(import/export): article import + register export (xlsx/csv)

Add CSV/Excel import for the article register (artiklar), mirroring the
existing customer/supplier import pipeline, plus Excel + CSV export for
articles, customers and suppliers.

Import (lib/import/articles + app/api/import/articles):
- Column auto-detection tuned to Fortnox/Visma/Bokio export headers,
  Swedish-decimal price parsing, VAT snapped to {0,6,12,25}, type/unit
  normalization.
- Dedup by article number then name; 23505 soft-skip; auto-number
  backfill; revenue-account override kept only when active, otherwise
  dropped with a warning (never mutates the chart of accounts).
- New "Artiklar" flow in the /import hub.

Export (app/api/export/* + lib/export/register-export):
- Read-only xlsx (default) / csv (?format=csv, UTF-8 BOM) downloads.
- Headers chosen so files round-trip back through the importer.
- "Exportera" menu added to the articles, customers and suppliers pages.

Refs #746. Direct Fortnox/Visma API article fetch tracked in #749.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(import/export): address PR review — lint ratchet + export hardening

- xlsx-export: keep `SheetSpec<any>` on the eslint-disabled line (fixes the
  core-only lint ratchet regression: no-explicit-any 16 -> 15) and define
  UTF8_BOM as an explicit `` escape instead of a raw BOM character.
- export routes (articles/customers/suppliers): move the data queries inside
  the try/catch, add `Cache-Control: no-store`, and emit a `register exported`
  audit log line (entity, format, rowCount).
- articles parse route: validate `column_overrides` against a Zod schema before
  trusting it to drive the parser.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(import): drop öre-round pattern on article column-detector confidence

The confidence score is a 0-1 heuristic, not money, and is only compared
against the 0.8 skip-mapping threshold. Removing the Math.round(x*100)/100
form clears the core-only antipattern ratchet (naive-ore-round 660 -> 659).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat(import): flag adjusted VAT rows in the article import edit step

Surface VAT snapping/defaulting per row, not just as a file-level warning:
the parser sets `vat_rate_adjusted`, the edit step highlights those rows'
VAT selector and shows a count banner, and confirming a rate clears the flag.
Addresses the Swedish-compliance review note that silent snapping could
otherwise store a wrong VAT rate at scale.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

components/reports/ReportExportMenu.tsx

@@ -1,6 +1,6 @@
 'use client'
 
-import { Download, FileSpreadsheet, FileText } from 'lucide-react'
+import { Download, FileSpreadsheet, FileText, Table } from 'lucide-react'
 import { useTranslations } from 'next-intl'
 import { Button } from '@/components/ui/button'
 import {
@@ -9,10 +9,12 @@ import {
   DropdownMenuItem,
   DropdownMenuTrigger,
 } from '@/components/ui/dropdown-menu'
-import type { ReportExportFormat } from '@/lib/reports/catalog'
+
+/** pdf/xlsx for reports; csv is additionally used by register exports. */
+export type ExportMenuFormat = 'pdf' | 'xlsx' | 'csv'
 
 export interface ReportExportItem {
-  format: ReportExportFormat
+  format: ExportMenuFormat
   href: string
 }
 
@@ -50,10 +52,16 @@ export function ReportExportMenu({
               >
                 {item.format === 'pdf' ? (
                   <FileText className="h-4 w-4 mr-2" />
+                ) : item.format === 'csv' ? (
+                  <Table className="h-4 w-4 mr-2" />
                 ) : (
                   <FileSpreadsheet className="h-4 w-4 mr-2" />
                 )}
-                {item.format === 'pdf' ? t('download_pdf') : t('download_excel')}
+                {item.format === 'pdf'
+                  ? t('download_pdf')
+                  : item.format === 'csv'
+                    ? t('download_csv')
+                    : t('download_excel')}
               </DropdownMenuItem>
             ))}
           </DropdownMenuContent>