Add organizer-only attendee list to event detail view (011)

New GET /events/{token}/attendees endpoint returns attendee names when
a valid organizer token is provided (403 otherwise). The frontend
conditionally renders the list below the attendee count for organizers,
silently degrading for visitors.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/main/resources/openapi/api.yaml

@@ -83,6 +83,47 @@ paths:
               schema:
                 $ref: "#/components/schemas/ProblemDetail"
 
+  /events/{token}/attendees:
+    get:
+      operationId: getAttendees
+      summary: Get attendee list for an event (organizer only)
+      tags:
+        - events
+      parameters:
+        - name: token
+          in: path
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Public event token
+        - name: organizerToken
+          in: query
+          required: true
+          schema:
+            type: string
+            format: uuid
+          description: Organizer token for authorization
+      responses:
+        "200":
+          description: Attendee list
+          content:
+            application/json:
+              schema:
+                $ref: "#/components/schemas/GetAttendeesResponse"
+        "403":
+          description: Invalid organizer token
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+        "404":
+          description: Event not found
+          content:
+            application/problem+json:
+              schema:
+                $ref: "#/components/schemas/ProblemDetail"
+
   /events/{token}:
     get:
       operationId: getEvent
@@ -256,6 +297,30 @@ components:
           description: Guest's display name as stored
           example: "Max Mustermann"
 
+    GetAttendeesResponse:
+      type: object
+      required:
+        - attendees
+      properties:
+        attendees:
+          type: array
+          items:
+            $ref: "#/components/schemas/Attendee"
+          example:
+            - name: "Alice"
+            - name: "Bob"
+
+    Attendee:
+      type: object
+      required:
+        - name
+      properties:
+        name:
+          type: string
+          minLength: 1
+          maxLength: 100
+          example: "Alice"
+
     ProblemDetail:
       type: object
       properties: