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)/backups/page.tsx

@@ -28,6 +28,7 @@ import { useDataSource } from "@/lib/data-source"
 import { listServers } from "@/shared/api/servers"
 import { toFrontendServer } from "@/entities/server/model/mappers"
 import { createBackupsAsync, deleteBackup, getBackupJob, getBackupScheduleSettings, listBackups, putBackupScheduleSettings, type BackupItem } from "@/shared/api/backups"
+import { requestBlob } from "@/shared/api/http-client"
 import { toast } from "sonner"
 import {
   Stepper,
@@ -276,8 +277,7 @@ export default function BackupsPage() {
   }
 
   async function handleDownload(id: string, fallbackFilename: string) {
-    const res = await fetch(`${backendUrl.replace(/\/$/, "")}/api/backups/${id}/download`)
-    if (!res.ok) throw new Error("Не удалось скачать файл")
+    const res = await requestBlob(backendUrl, `/api/backups/${id}/download`)
     const blob = await res.blob()
     const url = URL.createObjectURL(blob)
     const a = document.createElement("a")

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))

app/(main)/ospf/page.tsx

@@ -16,6 +16,7 @@ import {
 } from "lucide-react"
 import { cn } from "@/lib/utils"
 import { useDataSource } from "@/lib/data-source"
+import { requestJson } from "@/shared/api/http-client"
 import { Flag } from "@/components/flag"
 import { readStoredRouteOptimizerSettings } from "@/lib/route-optimizer-data"
 
@@ -733,13 +734,14 @@ function InterfacesTab({
     const ra = readStoredRouteOptimizerSettings()
     setOptimizing(true)
     try {
-      const r = await fetch(`${backendUrl}/api/servers/${filterServerId}/ospf/optimize`, {
-        method: "POST",
-        headers: { "Content-Type": "application/json" },
-        body: JSON.stringify({ pingWeight: ra.pingWeight }),
-      })
-      if (!r.ok) throw new Error(`HTTP ${r.status}`)
-      const data = await r.json() as BackendOspfOptimizeResponse
+      const data = await requestJson<BackendOspfOptimizeResponse>(
+        backendUrl,
+        `/api/servers/${filterServerId}/ospf/optimize`,
+        {
+          method: "POST",
+          body: JSON.stringify({ pingWeight: ra.pingWeight }),
+        },
+      )
       const byKey: Record<string, number> = {}
       data.interfaces.forEach((row) => {
         byKey[`${data.serverId}-${row.id}`] = row.optimalCost
@@ -1120,8 +1122,7 @@ export default function OspfPage() {
       if (cancelled) return
       setLoading(true)
       setLiveError(null)
-      fetch(`${backendUrl}/api/ospf/all`)
-        .then(r => { if (!r.ok) throw new Error(`HTTP ${r.status}`); return r.json() as Promise<BackendOspfAll> })
+      void requestJson<BackendOspfAll>(backendUrl, "/api/ospf/all")
         .then(data => {
           if (cancelled) return
           setLiveData(data); setFetchedAt(new Date()); setLoading(false)

app/(main)/terminal/page.tsx

@@ -6,6 +6,7 @@ import { Button } from "@/components/ui/button"
 import { servers as mockServers } from "@/lib/data"
 import { Flag } from "@/components/flag"
 import { useDataSource } from "@/lib/data-source"
+import { requestJson } from "@/shared/api/http-client"
 import {
   TrashIcon, RefreshCwIcon, CircleIcon, Loader2Icon,
 } from "lucide-react"
@@ -259,12 +260,14 @@ function Terminal({
     if (isLive && server.backendId !== null) {
       setExecuting(true)
       try {
-        const res  = await fetch(`${backendUrl}/api/servers/${server.backendId}/exec`, {
-          method:  "POST",
-          headers: { "Content-Type": "application/json" },
-          body:    JSON.stringify({ command: cmd }),
-        })
-        const data = await res.json() as { output?: string; error?: string }
+        const data = await requestJson<{ output?: string; error?: string }>(
+          backendUrl,
+          `/api/servers/${server.backendId}/exec`,
+          {
+            method: "POST",
+            body: JSON.stringify({ command: cmd }),
+          },
+        )
         const text = data.output ?? data.error ?? "(empty response)"
         const kind: TermLine["kind"] = text.startsWith("error:") ? "error" : "output"
         text.split("\n").forEach(line =>
@@ -427,7 +430,7 @@ interface BackendServer {
 }
 
 export default function TerminalPage() {
-  const { mode, backendUrl } = useDataSource()
+  const { mode, backendUrl, prefsHydrated } = useDataSource()
   const isLive = mode === "live"
 
   // Server list state
@@ -437,14 +440,13 @@ export default function TerminalPage() {
 
   // Load servers from backend when in live mode
   useEffect(() => {
-    if (!isLive) return
+    if (!isLive || !prefsHydrated) return
     let cancelled = false
     queueMicrotask(() => {
       if (cancelled) return
       setServersLoading(true)
-      fetch(`${backendUrl}/api/servers`)
-        .then(r => r.json() as Promise<BackendServer[]>)
-        .then(data => {
+      void requestJson<BackendServer[]>(backendUrl, "/api/servers")
+        .then((data) => {
           if (cancelled) return
           setLiveServers(data.map(s => ({
             uid:          String(s.id),
@@ -462,7 +464,7 @@ export default function TerminalPage() {
         .catch(() => { if (!cancelled) setServersLoading(false) })
     })
     return () => { cancelled = true }
-  }, [isLive, backendUrl, refreshKey])
+  }, [isLive, backendUrl, refreshKey, prefsHydrated])
 
   const termServers: TermServer[] = isLive ? liveServers : mockServersToTermServers()