feat: add bank file import as core, move Enable Banking to extension

Replace PSD2 bank integration as the default with file-based bank
import (CSV/XML), which better suits Swedish sole traders and small
companies. Enable Banking is now an opt-in extension.

- Phase 1: Extract generic transaction ingestion service (ingest.ts)
  with dedup, auto-categorization, and OCR-based invoice matching
- Phase 2: Bank file parser library supporting Nordea, SEB, Swedbank,
  Handelsbanken CSV formats and ISO 20022 camt.053 XML
- Phase 3: Database migration adding import_source, reference columns
  and bank_file_imports tracking table
- Phase 4: Import wizard UI (5-step flow) and API routes for parse/execute
- Phase 5: Move Enable Banking to extensions/enable-banking/ with
  commented-out loader entry for opt-in activation
- Phase 6: 104 new tests (ingestion + all parser formats), fixing
  Nordea detection overlap and camt.053 XML tag collision bugs

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

extensions/enable-banking/types.ts

@@ -0,0 +1,24 @@
+// Enable Banking extension types
+
+export interface StoredAccount {
+  uid: string
+  iban?: string
+  name?: string
+  currency: string
+  balance?: number
+}
+
+// Re-export API types from the client
+export type {
+  ASPSP,
+  AuthMethod,
+  AuthResponse,
+  SessionResponse,
+  AccountInfo,
+  Balance,
+  BalanceResponse,
+  Transaction as EnableBankingTransaction,
+  TransactionsResponse,
+  Bank,
+  BankTransaction,
+} from './lib/api-client'