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.

backend/src/services/system-database-backup.ts

@@ -0,0 +1,93 @@
+import { randomUUID } from "node:crypto"
+import { mkdir, readFile, rm, writeFile } from "node:fs/promises"
+import os from "node:os"
+import path from "node:path"
+import Database from "better-sqlite3"
+import { env } from "../config.js"
+import { sqliteDatabase } from "../db/index.js"
+import { refreshScheduler, stopScheduler } from "./scheduler.js"
+
+const SQLITE_MAGIC = Buffer.from("SQLite format 3\0")
+const MAX_RESTORE_BYTES = 512 * 1024 * 1024
+
+type SqliteHandle = InstanceType<typeof Database>
+
+let operationInFlight = false
+
+function fmtTimestamp(date = new Date()): string {
+  const pad = (n: number) => String(n).padStart(2, "0")
+  return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}_${pad(date.getHours())}-${pad(date.getMinutes())}-${pad(date.getSeconds())}`
+}
+
+function resolveDatabasePath(): string {
+  return path.resolve(process.cwd(), env.DATABASE_PATH)
+}
+
+function assertSqliteFile(buffer: Buffer): void {
+  if (buffer.length < SQLITE_MAGIC.length) {
+    throw new Error("Файл слишком маленький для SQLite")
+  }
+  if (!buffer.subarray(0, SQLITE_MAGIC.length).equals(SQLITE_MAGIC)) {
+    throw new Error("Файл не похож на резервную копию SQLite")
+  }
+}
+
+async function withDatabaseOperation<T>(fn: () => Promise<T> | T): Promise<T> {
+  if (operationInFlight) {
+    throw new Error("Операция с базой данных уже выполняется")
+  }
+  operationInFlight = true
+  stopScheduler()
+  try {
+    return await fn()
+  } finally {
+    refreshScheduler()
+    operationInFlight = false
+  }
+}
+
+export async function exportSystemDatabaseBackup(): Promise<{ filename: string; buffer: Buffer }> {
+  return withDatabaseOperation(async () => {
+    sqliteDatabase.pragma("wal_checkpoint(TRUNCATE)")
+    const tempDir = path.join(os.tmpdir(), "mmapp-db-backup")
+    await mkdir(tempDir, { recursive: true })
+    const tempPath = path.join(tempDir, `manager-${randomUUID()}.db`)
+    try {
+      await sqliteDatabase.backup(tempPath)
+      const buffer = await readFile(tempPath)
+      return {
+        filename: `mikrotik-manager_${fmtTimestamp()}.db`,
+        buffer,
+      }
+    } finally {
+      await rm(tempPath, { force: true })
+    }
+  })
+}
+
+export async function restoreSystemDatabaseBackup(buffer: Buffer): Promise<void> {
+  if (buffer.length > MAX_RESTORE_BYTES) {
+    throw new Error("Файл бэкапа слишком большой")
+  }
+  assertSqliteFile(buffer)
+
+  await withDatabaseOperation(async () => {
+    const tempDir = path.join(os.tmpdir(), "mmapp-db-restore")
+    await mkdir(tempDir, { recursive: true })
+    const tempPath = path.join(tempDir, `restore-${randomUUID()}.db`)
+    let source: SqliteHandle | null = null
+    try {
+      await writeFile(tempPath, buffer)
+      source = new Database(tempPath, { readonly: true, fileMustExist: true })
+      await source.backup(resolveDatabasePath())
+      sqliteDatabase.pragma("wal_checkpoint(TRUNCATE)")
+    } finally {
+      source?.close()
+      await rm(tempPath, { force: true })
+    }
+  })
+}
+
+export function getSystemDatabasePath(): string {
+  return resolveDatabasePath()
+}