docs(backlog): add FORM-05 smart identity-match on public submission values

dev-docs/BACKLOG.md

@@ -339,6 +339,26 @@ shifts claimen zonder toegang tot de Organizer app.
 
 ---
 
+### FORM-05 — Smart identity-match on public submission values
+
+Public form submissions (subject_type=null) currently always get
+identity_match_status='pending' because the listener needs a Person
+to match against and public submissions don't create one yet.
+
+Improve: when a public event_registration submission arrives, extract
+email + first_name + last_name from the submission values (via the
+schema's binding config) and call a new PersonIdentityService method:
+    detectMatchesByValues(array $values, string $organisationId): MatchResult
+
+Set identity_match_status to matched / pending / none based on actual
+lookup. This gives the portal-form UX a meaningful signal instead of
+a constant pending.
+
+Priority: Medium. Can bundle with organizer person_identity_matches UI
+(which is also still a frontend gap).
+
+---
+
 ### SUP-01 — Leveranciersportal + productieverzoeken
 
 **Aanleiding:** Leveranciers moeten productie-informatie kunnen indienen.