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>

specs/011-view-attendee-list/contracts/api.md

@@ -0,0 +1,136 @@
+# API Contract: View Attendee List (011)
+
+**Date**: 2026-03-08
+
+## New Endpoint
+
+### `GET /events/{token}/attendees`
+
+Retrieves the list of attendees for an event. Restricted to the event organizer.
+
+**Path Parameters**:
+
+| Parameter | Type | Description |
+|-----------|------|-------------|
+| token | string (UUID) | Event token |
+
+**Query Parameters**:
+
+| Parameter | Type | Required | Description |
+|-----------|------|----------|-------------|
+| organizerToken | string (UUID) | Yes | Organizer token for authorization |
+
+**Responses**:
+
+#### 200 OK
+
+Organizer token is valid. Returns the attendee list.
+
+```json
+{
+  "attendees": [
+    { "name": "Alice" },
+    { "name": "Bob" },
+    { "name": "Charlie" }
+  ]
+}
+```
+
+#### 200 OK (empty list)
+
+No RSVPs yet.
+
+```json
+{
+  "attendees": []
+}
+```
+
+#### 403 Forbidden
+
+Organizer token is missing, invalid, or does not match the event.
+
+```json
+{
+  "type": "about:blank",
+  "title": "Forbidden",
+  "status": 403,
+  "detail": "Invalid organizer token."
+}
+```
+
+#### 404 Not Found
+
+Event token does not exist.
+
+```json
+{
+  "type": "about:blank",
+  "title": "Not Found",
+  "status": 404,
+  "detail": "Event not found."
+}
+```
+
+## OpenAPI Schema Addition
+
+```yaml
+/events/{token}/attendees:
+  get:
+    operationId: getAttendees
+    summary: Get attendee list for an event (organizer only)
+    parameters:
+      - name: token
+        in: path
+        required: true
+        schema:
+          type: string
+          format: uuid
+      - name: organizerToken
+        in: query
+        required: true
+        schema:
+          type: string
+          format: uuid
+    responses:
+      '200':
+        description: Attendee list
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/GetAttendeesResponse'
+      '403':
+        description: Invalid organizer token
+      '404':
+        description: Event not found
+
+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"
+```
+
+## Existing Endpoints (unchanged)
+
+- `POST /events` — no changes
+- `GET /events/{token}` — no changes (still returns `attendeeCount` publicly)
+- `POST /events/{token}/rsvps` — no changes