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>

lib/extensions/loader.ts

@@ -7,6 +7,12 @@ import { neBilagaExtension } from '@/extensions/ne-bilaga'
 import { aiChatExtension } from '@/extensions/ai-chat'
 import type { Extension } from './types'
 
+// ── Enable Banking (PSD2) — opt-in extension ───────────────────────────
+// Uncomment the following line to enable automatic PSD2 bank transaction sync.
+// Requires ENABLE_BANKING_APP_ID and ENABLE_BANKING_PRIVATE_KEY env vars.
+//
+// import { enableBankingExtension } from '@/extensions/enable-banking'
+
 /**
  * Explicit list of first-party extensions.
  *
@@ -20,6 +26,7 @@ const FIRST_PARTY_EXTENSIONS: Extension[] = [
   sruExportExtension,
   neBilagaExtension,
   aiChatExtension,
+  // enableBankingExtension,  // Uncomment to activate PSD2 bank sync
 ]
 
 let loaded = false