refactor(api): streamline API requests with requestJson and requestBlob functions

Replaced direct fetch calls with requestJson and requestBlob utility functions across multiple components for improved consistency and error handling. This change enhances the maintainability of the codebase by centralizing API request logic and ensuring uniform handling of authentication and response parsing.

app/(main)/bgp/page.tsx

@@ -23,6 +23,7 @@ import {
   XIcon, AlertCircleIcon,
 } from "lucide-react"
 import { useDataSource } from "@/lib/data-source"
+import { requestJson } from "@/shared/api/http-client"
 
 // ─── types ────────────────────────────────────────────────────────────────────
 
@@ -621,11 +622,7 @@ export default function BgpPage() {
       if (cancelled) return
       setLoading(true)
       setLiveError(null)
-      fetch(`${backendUrl}/api/bgp/sessions`)
-        .then(r => {
-          if (!r.ok) throw new Error(`HTTP ${r.status}`)
-          return r.json() as Promise<BackendBgpSession[]>
-        })
+      void requestJson<BackendBgpSession[]>(backendUrl, "/api/bgp/sessions")
         .then(data => {
           if (cancelled) return
           setLiveSessions(data.map(backendToFrontend))