feat: assistant overview drilldown reports [CW-7408] (#14920)

<img width="2616" height="1716" alt="CleanShot 2026-07-09 at 14 22
42@2x"
src="https://github.com/user-attachments/assets/504e58df-0243-4cb9-a811-62504fdcb0ac"
/>

---------

Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>
Co-authored-by: Sony Mathew <sony@chatwoot.com>

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

@@ -37,6 +37,20 @@ class CaptainAssistant extends ApiClient {
       params: { range, timezone_offset: getTimezoneOffset() },
     });
   }
+
+  getDrilldown({ assistantId, metric, range, page, signal }) {
+    const requestConfig = {
+      params: {
+        metric,
+        range,
+        timezone_offset: getTimezoneOffset(),
+        page,
+      },
+    };
+    if (signal) requestConfig.signal = signal;
+
+    return axios.get(`${this.url}/${assistantId}/drilldown`, requestConfig);
+  }
 }
 
 export default new CaptainAssistant();