fix: Swedish VAT compliance — representation, domestic RC, full 26xx mapping, SIE (#206)

* feat: add INK2 declaration improvements, invoice delivery date, and Swedish compliance skills

Expand INK2 engine with full INK2S/INK2R support and improved SRU generation.
Add delivery_date field to invoices and corresponding PDF/migration support.
Add Claude skills for Swedish asset accounting, invoice compliance, SIE import/export, SRU filing, and tax planning.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: address PR review — map BAS 4500–4899, strip CRLF in SRU, document P3

- Map BAS accounts 4500–4599 (legoarbeten), 4700–4899 (diverse
  varuinköpskostnader) to SRU 7512 so they are not silently dropped
  from INK2R declarations
- Strip \r\n in sanitizeString to prevent CRLF injection in SRU fields
- Document P3 period suffix limitation for brutet räkenskapsår

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: correct BAS 4500-4599, 4700-4899 mapping from 7512 to 7511

Per the official BAS-to-SRU mapping, these account ranges are cost of
goods (legoarbeten, inkurans, svinn) and belong under 7511 (Råvaror
och förnödenheter), not 7512 (Handelsvaror). 7512 remains 4600-4699.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: Swedish VAT compliance — representation VAT, domestic RC, full BAS 26xx mapping, SIE encoding

- Representation expenses now default to reduced_12 VAT (ML 13 kap 24-25 §§);
  income tax deduction was abolished 2017 but VAT deduction at 12% remains
- Domestic reverse charge (byggtjänster etc.) uses 2647 instead of 2645,
  with distinct line descriptions for Swedish vs EU/non-EU RC
- VAT declaration maps all BAS 26xx variant accounts (egna uttag 2612/2622/2632,
  uthyrning 2613/2623/2633, VMB 2616/2626/2636, import 2615/2625/2635,
  domestic RC 2647, frivillig skattskyldighet 2642) and revenue variants
  (3108/3105/3004/3100) to correct momsdeklaration rutor
- SIE parser: remove unreliable #FORMAT PC8 encoding detection (most software
  exports UTF-8 with PC8 header), parse #FLAGGA for import-already-done warning,
  default SIE type to 1 when absent, fix RTRANS/BTRANS documentation
- SIE export: add #RAR -1 (previous fiscal year), fix UB = IB + movements
- Error messages: add pattern matching for locked period trigger errors

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: address Greptile review — update ruta49 JSDoc, use null sentinel in error map

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

lib/errors/get-error-message.ts

@@ -66,6 +66,38 @@ const CONTEXT_FALLBACKS: Record<ErrorContext, string> = {
 
 const GENERIC_FALLBACK = 'Något gick fel. Försök igen.'
 
+// Known error patterns → user-friendly Swedish messages
+const ERROR_PATTERN_MAP: [RegExp, string | null][] = [
+  [
+    /locked\/closed fiscal period/i,
+    'Perioden är låst. Verifikationen kan inte skapas i en stängd eller låst period.',
+  ],
+  [
+    /Bokföringen är låst t\.o\.m\./,
+    null, // null = extract the Swedish message directly from the raw error text
+  ],
+  [
+    /Cannot attach documents to entries in a locked/i,
+    'Kan inte bifoga dokument till verifikationer i en låst period.',
+  ],
+]
+
+/**
+ * Check if a message matches a known error pattern and return the Swedish translation.
+ * Returns null if no pattern matches.
+ */
+function tryMatchKnownError(message: string): string | null {
+  for (const [pattern, translation] of ERROR_PATTERN_MAP) {
+    if (pattern.test(message)) {
+      if (translation !== null) return translation
+      // Extract the Swedish part from the message
+      const match = message.match(/Bokföringen är låst t\.o\.m\. [^.]+\./)
+      return match ? match[0] : 'Bokföringen är låst för denna period.'
+    }
+  }
+  return null
+}
+
 /**
  * Simple heuristic to detect already-translated Swedish messages.
  * If the message contains common Swedish words/patterns, pass it through.
@@ -83,6 +115,7 @@ function isSwedishUserMessage(message: string): boolean {
     /session/i,
     /förfrågan/i,
     /obligatorisk/i,
+    /bokföringen är låst/i,
   ]
   return swedishPatterns.some((p) => p.test(message))
 }
@@ -155,6 +188,14 @@ export function getErrorMessage(
       return POSTGRES_ERROR_MAP[obj.code]
     }
 
+    // Try known error patterns (e.g. locked period triggers)
+    for (const field of ['error', 'message'] as const) {
+      if (typeof obj[field] === 'string' && obj[field].trim()) {
+        const knownError = tryMatchKnownError(obj[field])
+        if (knownError) return knownError
+      }
+    }
+
     // Try error.message if it's already a good Swedish message
     if (typeof obj.error === 'string' && obj.error.trim()) {
       if (isSwedishUserMessage(obj.error)) return obj.error
@@ -167,6 +208,8 @@ export function getErrorMessage(
 
   // 3. Error instance
   if (error instanceof Error && error.message.trim()) {
+    const knownError = tryMatchKnownError(error.message)
+    if (knownError) return knownError
     if (isSwedishUserMessage(error.message)) return error.message
   }