feature: Add Berlin Group PSD2 signature support

[constantine2nd]

Files Created

1. server/types/berlin-group.ts

   • TypeScript interfaces: BerlinGroupConfig, BerlinGroupHeaders, BerlinGroupSessionData

2. server/services/BerlinGroupSignatureService.ts

   • New @service() class that: - Loads private key and certificate PEM files from VITE_BG_PRIVATE_KEY_PATH and VITE_BG_CERTIFICATE_PATH at construction - isEnabled() checks if certificates are loaded - static isBerlinGroupPath(path) detects "/berlin-group/" in request paths - generateHeaders(method, body, consentId?) generates required PSD2 headers: Date X-Request-ID Digest (SHA-256) Signature (RSA-SHA256) TPP-Signature-Certificate PSU headers Redirect URIs (POST only) Optional Consent-ID

Files Modified

3. server/services/OBPClientService.ts
   • get(), create(), update(), discard() now check isBerlinGroupPath() && isEnabled()
   • Routes Berlin Group requests to new private method requestWithBerlinGroupHeaders()
   • Merges signature headers with op