feat(invoices): implement öresavrundning logic and next invoice numbe… (#429)

* feat(invoices): implement öresavrundning logic and next invoice number preview

- Added `getDisplayTotal` utility to handle rounding for SEK invoices based on company settings.
- Updated `InvoicesPage` to utilize the new rounding logic when displaying totals.
- Introduced `peek_next_invoice_number` function to allow previewing the next invoice number without consuming the sequence.
- Modified invoice number generation to remove the year prefix and prevent truncation of numbers exceeding three digits.
- Enhanced tests for invoice number generation and rounding functionality to ensure correctness.
- Updated PDF template to reflect new rounding logic for totals and display appropriate values.
- Adjusted company switcher to hide options in sandbox mode.
- Improved error handling and logging in sandbox seeding process.

* fix(skatteverket): remove unused scope labels from SCOPE_LABELS and DEFAULT_SCOPES

app/api/invoices/next-number/route.ts

@@ -0,0 +1,38 @@
+import { NextResponse } from 'next/server'
+import { withRouteContext } from '@/lib/api/with-route-context'
+import { errorResponse } from '@/lib/errors/get-structured-error'
+
+export const GET = withRouteContext(
+  'invoice.peek_next_number',
+  async (request, ctx) => {
+    const { supabase, companyId, log, requestId } = ctx
+
+    const url = new URL(request.url)
+    const documentType = url.searchParams.get('document_type') ?? 'invoice'
+    if (!['invoice', 'proforma', 'delivery_note'].includes(documentType)) {
+      return NextResponse.json(
+        { error: 'invalid document_type', requestId },
+        { status: 400 },
+      )
+    }
+
+    // delivery_note has its own sequence (generate_delivery_note_number); the
+    // peek RPC only covers the invoice/proforma F-series counter, so for
+    // delivery notes we return null and let the form skip the preview.
+    if (documentType === 'delivery_note') {
+      return NextResponse.json({ data: { preview: null } })
+    }
+
+    const { data, error } = await supabase.rpc('peek_next_invoice_number', {
+      p_company_id: companyId,
+      p_document_type: documentType,
+    })
+
+    if (error) {
+      log.error('peek_next_invoice_number failed', error)
+      return errorResponse(error, log, { requestId })
+    }
+
+    return NextResponse.json({ data: { preview: data ?? null } })
+  },
+)