feat: Mini-Apps registry, Stammdaten backend persistence, bank accounts

- Register 6 mini-apps in kommunikation plugin (contact_picker, file_share,
  calendar_invite, mail_forward, ai_search, task_create)
- Connect AdressenTab to backend API (GET/POST/PATCH/DELETE /addresses)
- Create BankAccount model, schema, service, routes + migration 0033
- Connect KontenTab to backend API (GET/POST/PATCH/DELETE /bank-accounts)
- AI tools already working: 7 tools registered (hybrid_search, get_contact_mails, etc.)

app/routes/__init__.py

@@ -3,6 +3,7 @@
 from app.routes import (
     addresses,  # noqa: F401
     ai_copilot,  # noqa: F401
+    bank_accounts,  # noqa: F401
     audit,  # noqa: F401
     auth,  # noqa: F401
     contacts,  # noqa: F401