refactor(fe): align dashboard with backend & gateway data flow

- API/WS clients: same-origin by default, drop dead imphnen hardcode
- chatbot history: map BE rows {user_message,bot_response,created_at}
- message_deleted WS payload: object {id,deleted_at}, not bare string
- dashboard: wire top-channels chart + live mod queue from /api/review,
  add Users & Channels tabs consuming /api/dashboard/users|channels
- recordings: live WS sync via voice_recording_uploaded; duration_bytes optional
- remove dead widgets with no BE data source (trend chart, heatmap)

services/frontend/src/lib/api/chatbot.ts

@@ -1,11 +1,14 @@
-import type { ChatbotResponse, ChatHistoryMessage } from "@/lib/types";
+import type { ChatbotHistoryRow, ChatbotResponse } from "@/lib/types";
 import { api } from "./client";
 
 export const chatbotApi = {
   send: (message: string) =>
     api.post<ChatbotResponse>("/api/chat", { message }),
 
-  getHistory: () => api.get<ChatHistoryMessage[]>("/api/chat/history"),
+  getHistory: () =>
+    api.get<{ history: ChatbotHistoryRow[]; total: number }>(
+      "/api/chat/history",
+    ),
 
   clearHistory: () => api.delete<{ ok: boolean }>("/api/chat/history"),
 };