feat: implement database backup and restore functionality in settings page

- Added UI components for downloading and restoring the application database, enhancing data management capabilities.
- Integrated new API routes for system database operations in the backend.
- Implemented state management for backup and restore processes, including loading indicators and user notifications.

shared/api/system-database.ts

@@ -0,0 +1,60 @@
+import { ApiClientError } from "@/shared/api/http-client"
+
+function trimBaseUrl(baseUrl: string): string {
+  return baseUrl.replace(/\/$/, "")
+}
+
+function parseFilename(contentDisposition: string | null, fallback: string): string {
+  if (!contentDisposition) return fallback
+  const utfMatch = /filename\*=UTF-8''([^;]+)/i.exec(contentDisposition)
+  if (utfMatch?.[1]) {
+    try {
+      return decodeURIComponent(utfMatch[1])
+    } catch {
+      return utfMatch[1]
+    }
+  }
+  const plainMatch = /filename="([^"]+)"/i.exec(contentDisposition)
+  if (plainMatch?.[1]) return plainMatch[1]
+  return fallback
+}
+
+export async function downloadSystemDatabaseBackup(
+  baseUrl: string,
+): Promise<{ blob: Blob; filename: string }> {
+  const res = await fetch(`${trimBaseUrl(baseUrl)}/api/system/database/backup`)
+  if (!res.ok) {
+    const payload = await res.json().catch(() => undefined)
+    const msg =
+      typeof payload === "object" &&
+      payload !== null &&
+      "error" in payload &&
+      typeof (payload as { error?: unknown }).error === "string"
+        ? (payload as { error: string }).error
+        : res.statusText
+    throw new ApiClientError(msg, res.status, payload)
+  }
+  const blob = await res.blob()
+  const filename = parseFilename(res.headers.get("Content-Disposition"), "mikrotik-manager.db")
+  return { blob, filename }
+}
+
+export async function restoreSystemDatabaseBackup(baseUrl: string, file: File): Promise<void> {
+  const body = await file.arrayBuffer()
+  const res = await fetch(`${trimBaseUrl(baseUrl)}/api/system/database/restore`, {
+    method: "POST",
+    headers: { "Content-Type": "application/octet-stream" },
+    body,
+  })
+  if (!res.ok) {
+    const payload = await res.json().catch(() => undefined)
+    const msg =
+      typeof payload === "object" &&
+      payload !== null &&
+      "error" in payload &&
+      typeof (payload as { error?: unknown }).error === "string"
+        ? (payload as { error: string }).error
+        : res.statusText
+    throw new ApiClientError(msg, res.status, payload)
+  }
+}