Django admin action: run/refresh Wikidata property sync on demand

[gregoryfoster]

Background

sync_wikidata_properties is currently only runnable via the management command CLI. Operators need a way to trigger a refresh from the Django admin without SSH access — for example, after Wikidata adds new identifier properties relevant to persons, or to re-sync after enabling new ExternalPlatform entries.

Related to #33 (auto-sync on first run).

Proposed feature

Add a custom Django admin action (or admin view) on ExternalIdentifierPropertyAdmin that:

1. Runs sync_wikidata_properties logic inline (extracted to a callable in models.py or a service module so both the management command and admin action can call it).
2. Displays a confirmation page before executing (since the operation takes ~5–10 min and makes external SPARQL calls).
3. Reports results: rows created, rows updated, rows unchanged, duration.
4. Locks out concurrent runs (atomic flag or DB row lock) to prevent double-execution.

Design note

The sync command logic should be extracted from the management command into a sync_wikidata_properties() service function in src/core/ or src/web/persons/services.py — keeping the management command as a thin wrapper. This makes it callable from the admin action, tests, and future cron tasks (#28) without duplicating SPARQL logic.

Acceptance criteria

• Service function extracted; management command delegates to it.
• Admin action visible on the ExternalIdentifierProperty changelist.
• Confirmation page shown before execution.
• Result summary (created/updated/unchanged/duration) displayed in admin message on completion.
• Concurrent-run guard in place.
• Tests cover the service function; admin action has at least a smoke test.