test(persons): verify SoftDeletes behaviour per WS-1 finding D-05

Pre-flight audit verified the implementation was already in place,
so this commit is test-only (as the task prompt allowed):
- api/database/migrations/2026_04_08_220000_create_persons_table.php:27
  already carries $table->softDeletes().
- api/app/Models/Person.php lines 18 + 24 already use the SoftDeletes trait.

No production code change required.

tests/Feature/Person/PersonSoftDeleteTest.php pins the documented
behaviour so WS-6 (FormBindingApplicator + ARTIST_ADVANCE /
EVENT_REGISTRATION workflows) can rely on it without a second
verification pass:
- delete() sets deleted_at and excludes the row from default queries
- Person::withTrashed()->find($id) returns the soft-deleted row
- Person::onlyTrashed()->count() reports accurately
- restore() clears deleted_at
- forceDelete() removes the row permanently

PersonPolicy was spot-checked alongside the audit; existing view/update/
delete methods do not invoke withTrashed() on controller resolution.
That's acceptable today — no caller relies on editing a trashed Person —
so AUTH_ARCHITECTURE.md is left unchanged. If a restore-workflow lands
in a future sprint, the controller binding will need to switch to
->withTrashed() and the behaviour deserves a dedicated doc paragraph
then.

Minor path note: the task prompt specified
tests/Feature/Persons/PersonSoftDeleteTest.php (plural), but the
existing convention in this repo is tests/Feature/Person/ (singular).
Matched the existing directory rather than introducing a singular/plural
split.

Also carries the BACKLOG DOC-04 entry Bert asked for during WS-4 review:
scripts/install-claude-sync-hooks.sh belongs in SETUP.md / onboarding
so new clones don't miss the post-commit sync hook.

5 tests / 10 new assertions. Full suite: 1005 passed (2716 assertions).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dev-docs/BACKLOG.md

@@ -373,6 +373,19 @@ form-builder UI), omdat screenshots pas zin hebben als de UI staat.
 
 ---
 
+### DOC-04 — `scripts/install-claude-sync-hooks.sh` opnemen in SETUP/onboarding
+
+**Aanleiding:** WS-4 pre-flight audit vond dat `scripts/sync-claude-docs.sh`
+bestaat en door de post-commit hook draait, maar de hook-installer
+(`scripts/install-claude-sync-hooks.sh`) is niet terug te vinden in de
+developer onboarding-instructies. Nieuwe clones missen de hook.
+**Wat:** Voeg een regel aan `dev-docs/SETUP.md` (of een post-install
+checklist) toe die nieuwe developers opdraagt `install-claude-sync-hooks.sh`
+te runnen. 1 regel, geen scope-impact.
+**Prioriteit:** Laag — nice-to-have, niet blokkerend voor dev of CI.
+
+---
+
 ### FORM-05 — Smart identity-match on public submission values
 
 **Stub-status (S3a PR 2, 2026-04-23):** Public event_registration