Fix admin person view: add entryId migration for existing data

- Added migration in local store: on app start, iterate over all citizens and
  assign a unique entryId (string) to any ledger entry missing one. This ensures
  that defer, edit, and delete buttons work correctly even with data imported
  before the entryId feature was introduced.
- Updated bulk import and bulk append functions to always generate entryId for
  new entries.
- Verified that all admin detail actions (add contribution, record payment,
  forgive, defer, edit, delete, mark fully paid) now work reliably.
- This resolves the "nothing inside admin person view is working" issue for
  users with existing data.

Author: enga018