feat: register export sector with 4 extension definitions

Add export & utrikeshandel sector to the extension system with BAS
accounts (3105, 3108, 3109, 3521, 3522), sector metadata, icon
imports, workspace registry entries, and design document.

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

lib/extensions/loader.ts

@@ -6,6 +6,10 @@ import { sruExportExtension } from '@/extensions/sru-export'
 import { neBilagaExtension } from '@/extensions/ne-bilaga'
 import { aiChatExtension } from '@/extensions/general/ai-chat'
 import { invoiceInboxExtension } from '@/extensions/general/invoice-inbox'
+import { euSalesListExtension } from '@/extensions/export/eu-sales-list'
+import { vatMonitorExtension } from '@/extensions/export/vat-monitor'
+import { intrastatExtension } from '@/extensions/export/intrastat'
+import { currencyReceivablesExtension } from '@/extensions/export/currency-receivables'
 import type { Extension } from './types'
 
 // ── Enable Banking (PSD2) — opt-in extension ───────────────────────────
@@ -29,6 +33,12 @@ const FIRST_PARTY_EXTENSIONS: Extension[] = [
   aiChatExtension,
   invoiceInboxExtension,
   // enableBankingExtension,  // Uncomment to activate PSD2 bank sync
+
+  // ── Export sector ──────────────────────────────────────────
+  euSalesListExtension,
+  vatMonitorExtension,
+  intrastatExtension,
+  currencyReceivablesExtension,
 ]
 
 let loaded = false