feat(114): accounting configs refactor + invoice configs CRUD

Phase 114 complete (v3.7 Invoices):
- /settings/accounting jako hub-rozdroze (Paragony / Faktury)
- /settings/accounting/receipts + /invoices osobne podstrony list i edycji
- InvoiceConfigRepository + Controller (CRUD z walidacja delegacji)
- Seed Domyslny VAT (NOT EXISTS idempotent)
- invoice-config-form.js (toggle is_delegated -> integration_id)
- confirm-delete.js (globalny modul OrderProAlerts.confirm)
- Legacy aliasy starych endpointow /settings/accounting/save|toggle|delete

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.paul/codebase/db_schema.md

@@ -624,6 +624,8 @@ UNIQUE: `(config_id, year, month)`
 
 ## Invoices (Phase 113-01)
 
+> **Seed (Phase 114-01):** migration `20260511_000107_seed_default_invoice_config.sql` inserts a default `Domyslny VAT` config (format `FV/%N/%M/%Y`, monthly numbering, `is_delegated=0`, `payment_to_days=7`) idempotently via `NOT EXISTS` guard.
+
 **invoice_configs** — Invoice generation configurations (analogous to `receipt_configs` plus delegation flag)
 | Column | Type | Nullable | Notes |
 |--------|------|----------|-------|