feat: add "Lid toevoegen als deelnemer" shortcut for org members

Adds two new API endpoints to quickly add organisation members as event
persons with user_id pre-linked and status approved:
- GET /organisations/{org}/members/available-for-event/{event}
- POST /organisations/{org}/events/{event}/persons/from-member

Includes frontend dialog with member search, crowd type selection, and
click-to-add behavior in the Personen tab.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dev-docs/API.md

@@ -355,6 +355,50 @@ Validates:
 - `PUT /organisations/{org}/events/{event}/persons/{person}`
 - `POST /organisations/{org}/events/{event}/persons/{person}/approve`
 - `DELETE /organisations/{org}/events/{event}/persons/{person}`
+- `POST /organisations/{org}/events/{event}/persons/from-member` — create person from org member
+- `GET /organisations/{org}/members/available-for-event/{event}` — list members not yet added to event
+
+### Create Person from Member
+
+`POST /organisations/{org}/events/{event}/persons/from-member`
+
+Creates a Person record from an existing organisation member. The person is created with `status: approved` and `user_id` pre-linked.
+
+```json
+{
+  "user_id": "01JXYZ...",
+  "crowd_type_id": "01JXYZ..."
+}
+```
+
+Person data (first_name, last_name, email) is copied from the user account. Returns `PersonResource` (201).
+
+**Validation:**
+- User must belong to the organisation
+- User must not already be a person at this event (422)
+- crowd_type_id must belong to the organisation
+
+### Available Members for Event
+
+`GET /organisations/{org}/members/available-for-event/{event}`
+
+Returns organisation members who do NOT yet have a Person record at the specified event. Used to populate the "Lid toevoegen" dialog.
+
+```json
+{
+  "data": [
+    {
+      "id": "01JXYZ...",
+      "first_name": "Jan",
+      "last_name": "de Vries",
+      "full_name": "Jan de Vries",
+      "email": "jan@example.nl"
+    }
+  ]
+}
+```
+
+Auth: org member or higher on the organisation.
 
 ## Identity Matches