feat(invoicing): artikelregister (product/article catalog) with per-article revenue account (#703)

* feat(invoicing): artikelregister (product/article catalog) with per-article revenue account

Add a lean, non-inventory article catalog (artikelregister) so users can define
reusable invoice-line presets (name, unit, price excl VAT, VAT rate) with an
optional per-article BAS class-3 revenue-account override.

- DB: articles table (RLS via user_company_ids(), audit + updated_at triggers,
  unique-per-company article_number), generate_article_number RPC (atomic +
  idempotent), company_settings counter, nullable invoice_items.revenue_account
  + article_id, pending_operations CHECK expansion.
- Engine: generatePerRateLines groups revenue by (vat_rate, account) —
  byte-identical with no override, balance-safe when split (last account absorbs
  the rounding remainder), reverse_charge/export still force 3308/3305.
- API: /api/articles CRUD (soft-deactivate); override validated against
  chart_of_accounts (active class-3) and frozen onto invoice lines at create.
- Propagation: override carried through send/mark-sent/credit/convert/cash and
  the staged commit paths (recurring deferred — documented inline).
- MCP: gnubok_list/create/update_article (staged, scoped, risk-tiered).
- UI: articles register (list/detail/form) + nav + bilingual i18n + invoice-line
  article picker & "Spara som artikel" quick-create.
- Tests: engine regression, route, and pg-real (RPC/RLS/triggers).

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

* fix(mcp): strip ILIKE _ wildcard from gnubok_list_articles search

Underscore is a single-character ILIKE wildcard; stripping it (alongside the
existing %,()\* set) keeps a stray char in the article search from matching
every row. Read-only + RLS-scoped, so no security impact — addresses PR #703
reviewer + compliance-swarm CC6.3 notes.

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/dashboard/DashboardNav.tsx

@@ -29,6 +29,7 @@ import {
   ClipboardCheck,
   HandCoins,
   Package,
+  Tag,
   ChevronsUpDown,
   Sparkles,
 } from 'lucide-react'
@@ -81,6 +82,7 @@ type NavLabelKey =
   | 'invoice_inbox'
   | 'invoices'
   | 'customers'
+  | 'articles'
   | 'supplier_invoices'
   | 'suppliers'
   | 'review'
@@ -128,6 +130,7 @@ const navItems: NavItem[] = [
   // Försäljning dropdown
   { href: '/invoices', labelKey: 'invoices', icon: Receipt, group: 'försäljning' },
   { href: '/customers', labelKey: 'customers', icon: Users, group: 'försäljning' },
+  { href: '/articles', labelKey: 'articles', icon: Tag, group: 'försäljning' },
   // Inköp dropdown
   { href: '/supplier-invoices', labelKey: 'supplier_invoices', icon: Wallet, group: 'inköp' },
   { href: '/suppliers', labelKey: 'suppliers', icon: Building2, group: 'inköp' },