fix: anchor captain overview ranges to the viewer timezone

app/javascript/dashboard/api/captain/assistant.js

@@ -1,6 +1,10 @@
 /* global axios */
 import ApiClient from '../ApiClient';
 
+// Viewer's UTC offset in hours, matching the reports API convention so the
+// backend can anchor calendar ranges to the viewer's day.
+const getTimezoneOffset = () => -new Date().getTimezoneOffset() / 60;
+
 class CaptainAssistant extends ApiClient {
   constructor() {
     super('captain/assistants', { accountScoped: true });
@@ -23,12 +27,14 @@ class CaptainAssistant extends ApiClient {
   }
 
   getStats({ assistantId, range }) {
-    return axios.get(`${this.url}/${assistantId}/stats`, { params: { range } });
+    return axios.get(`${this.url}/${assistantId}/stats`, {
+      params: { range, timezone_offset: getTimezoneOffset() },
+    });
   }
 
   getSummary({ assistantId, range }) {
     return axios.get(`${this.url}/${assistantId}/summary`, {
-      params: { range },
+      params: { range, timezone_offset: getTimezoneOffset() },
     });
   }
 }