refactor: consolidate lib/invoice/ into lib/invoices/

Merge the singular lib/invoice/ directory into the plural lib/invoices/
to align with the codebase convention (transactions/, extensions/, reports/, etc.).
Updates all import paths and CLAUDE.md architecture docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -74,8 +74,7 @@ lib/
   events/                 Event bus (bus.ts, types.ts)
   extensions/             Extension registry, loader, types
   import/                 SIE and bank file parser
-  invoice/                VAT rules for invoicing
-  invoices/               Invoice business logic helpers
+  invoices/               Invoice helpers (VAT rules, PDF template, matching, reminders)
   reports/                Financial reports (trial-balance, income-statement,
                           balance-sheet, vat-declaration, sie-export,
                           supplier-ledger, supplier-reconciliation,
@@ -266,7 +265,7 @@ All defined in `lib/events/types.ts`:
 
 ### Scope
 
-Only test business logic in `lib/`. No component tests, no API route tests, no E2E tests.
+Test business logic in `lib/` and API routes in `app/api/`. No component tests, no E2E tests.
 
 ### Framework
 
@@ -302,6 +301,14 @@ mockResult({ data: makeTransaction(), error: null })
 - Test error paths (missing fiscal period, unbalanced entries)
 - Verify events are emitted correctly
 
+### API Route Tests
+
+- Colocated `__tests__/` directories alongside route files (e.g., `app/api/invoices/__tests__/route.test.ts`)
+- Mock `@/lib/supabase/server`, `@/lib/init`, and lib functions — do NOT re-test lib business logic
+- Use `createMockRequest()`, `parseJsonResponse()`, `createMockRouteParams()` from `tests/helpers.ts`
+- Use `createQueuedMockSupabase()` for routes with multiple sequential Supabase calls
+- Test: auth (401), validation (400), not found (404), errors (500), happy path, non-blocking journal entry failures
+
 ### Reference Tests
 
 - `lib/bookkeeping/__tests__/engine.test.ts` — Balance validation

app/(dashboard)/invoices/[id]/credit/page.tsx

@@ -10,7 +10,7 @@ import { Label } from '@/components/ui/label'
 import { Separator } from '@/components/ui/separator'
 import { useToast } from '@/components/ui/use-toast'
 import { formatCurrency, formatDate } from '@/lib/utils'
-import { getVatTreatmentLabel } from '@/lib/invoice/vat-rules'
+import { getVatTreatmentLabel } from '@/lib/invoices/vat-rules'
 import { Loader2, ArrowLeft, AlertTriangle } from 'lucide-react'
 import type { Invoice, InvoiceItem, Customer } from '@/types'
 

app/(dashboard)/invoices/[id]/page.tsx

@@ -10,7 +10,7 @@ import { Badge } from '@/components/ui/badge'
 import { Separator } from '@/components/ui/separator'
 import { useToast } from '@/components/ui/use-toast'
 import { formatCurrency, formatDate } from '@/lib/utils'
-import { getVatTreatmentLabel } from '@/lib/invoice/vat-rules'
+import { getVatTreatmentLabel } from '@/lib/invoices/vat-rules'
 import {
   Loader2,
   ArrowLeft,

app/(dashboard)/invoices/new/page.tsx

@@ -16,7 +16,7 @@ import { Select, SelectContent, SelectItem, SelectTrigger, SelectValue } from '@
 import { Separator } from '@/components/ui/separator'
 import { useToast } from '@/components/ui/use-toast'
 import { formatCurrency } from '@/lib/utils'
-import { getVatRules, getVatTreatmentLabel } from '@/lib/invoice/vat-rules'
+import { getVatRules, getVatTreatmentLabel } from '@/lib/invoices/vat-rules'
 import { Loader2, Plus, Trash2, ArrowLeft } from 'lucide-react'
 import { ConfirmationDialog } from '@/components/ui/confirmation-dialog'
 import { InvoiceReviewContent } from '@/components/invoices/InvoiceReviewContent'

app/api/invoices/[id]/pdf/route.ts

@@ -1,7 +1,7 @@
 import { createClient } from '@/lib/supabase/server'
 import { NextResponse } from 'next/server'
 import { renderToBuffer } from '@react-pdf/renderer'
-import { InvoicePDF } from '@/lib/invoice/pdf-template'
+import { InvoicePDF } from '@/lib/invoices/pdf-template'
 import type { Invoice, InvoiceItem, Customer, CompanySettings } from '@/types'
 
 export async function GET(

app/api/invoices/[id]/send/route.ts

@@ -3,7 +3,7 @@ import { NextResponse } from 'next/server'
 import { eventBus } from '@/lib/events'
 import { ensureInitialized } from '@/lib/init'
 import { renderToBuffer } from '@react-pdf/renderer'
-import { InvoicePDF } from '@/lib/invoice/pdf-template'
+import { InvoicePDF } from '@/lib/invoices/pdf-template'
 import { sendEmail, isResendConfigured } from '@/lib/email/resend'
 import {
   generateInvoiceEmailHtml,

app/api/invoices/route.ts

@@ -3,7 +3,7 @@ import { NextResponse } from 'next/server'
 import { eventBus } from '@/lib/events'
 import { ensureInitialized } from '@/lib/init'
 import type { CreateInvoiceInput, EntityType, Invoice, CreditNote } from '@/types'
-import { getVatRules, calculateVat, calculateTotal } from '@/lib/invoice/vat-rules'
+import { getVatRules, calculateVat, calculateTotal } from '@/lib/invoices/vat-rules'
 import { fetchExchangeRate, convertToSEK } from '@/lib/currency/riksbanken'
 import {
   createCreditNoteJournalEntry,

app/api/transactions/batch-match-invoices/route.ts

@@ -1,6 +1,6 @@
 import { createClient } from '@/lib/supabase/server'
 import { NextResponse } from 'next/server'
-import { getBestInvoiceMatch } from '@/lib/invoice/invoice-matching'
+import { getBestInvoiceMatch } from '@/lib/invoices/invoice-matching'
 import type { Transaction } from '@/types'
 
 /**

components/invoices/InvoiceReviewContent.tsx

@@ -2,7 +2,7 @@
 
 import { Badge } from '@/components/ui/badge'
 import { Separator } from '@/components/ui/separator'
-import { getVatTreatmentLabel } from '@/lib/invoice/vat-rules'
+import { getVatTreatmentLabel } from '@/lib/invoices/vat-rules'
 import { formatCurrency } from '@/lib/utils'
 import type { Customer, Currency, VatTreatment } from '@/types'
 

lib/transactions/__tests__/ingest.test.ts

@@ -26,7 +26,7 @@ vi.mock('@/lib/bookkeeping/transaction-entries', () => ({
 }))
 
 const mockGetBestInvoiceMatch = vi.fn()
-vi.mock('@/lib/invoice/invoice-matching', () => ({
+vi.mock('@/lib/invoices/invoice-matching', () => ({
   getBestInvoiceMatch: (...args: unknown[]) => mockGetBestInvoiceMatch(...args),
 }))
 

lib/transactions/ingest.ts

@@ -1,7 +1,7 @@
 import type { SupabaseClient } from '@supabase/supabase-js'
 import { evaluateMappingRules } from '@/lib/bookkeeping/mapping-engine'
 import { createTransactionJournalEntry } from '@/lib/bookkeeping/transaction-entries'
-import { getBestInvoiceMatch } from '@/lib/invoice/invoice-matching'
+import { getBestInvoiceMatch } from '@/lib/invoices/invoice-matching'
 import type { Transaction } from '@/types'
 
 /**