Replace logbook backup v1 JSON with v2 ZIP archives.

ZIP .daagbok files use a compact manifest and binary KDAB blobs so large
photo, voice, and GPS payloads no longer inflate in a single JSON file.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/services/logbookBackup/zipArchive.ts

@@ -0,0 +1,45 @@
+import { strToU8, unzipSync, zipSync } from 'fflate'
+import { parseManifestJson, type BackupManifestV2 } from './manifest.js'
+
+const ZIP_LEVEL = 6
+
+export function buildZipArchive(files: Record<string, Uint8Array>): Uint8Array {
+  return zipSync(files, { level: ZIP_LEVEL })
+}
+
+export function unzipArchive(data: Uint8Array): Record<string, Uint8Array> {
+  try {
+    return unzipSync(data)
+  } catch {
+    throw new Error('BACKUP_INVALID_ARCHIVE')
+  }
+}
+
+export function readManifestFromArchive(
+  files: Record<string, Uint8Array>
+): BackupManifestV2 {
+  const raw = files['manifest.json']
+  if (!raw) throw new Error('BACKUP_INVALID_FORMAT')
+  const text = new TextDecoder().decode(raw)
+  return parseManifestJson(text)
+}
+
+export function readTextFile(files: Record<string, Uint8Array>, path: string): string {
+  const raw = files[path]
+  if (!raw) throw new Error('BACKUP_MISSING_BLOB')
+  return new TextDecoder().decode(raw)
+}
+
+export function readBinaryFile(files: Record<string, Uint8Array>, path: string): Uint8Array {
+  const raw = files[path]
+  if (!raw) throw new Error('BACKUP_MISSING_BLOB')
+  return raw
+}
+
+export function utf8Bytes(text: string): Uint8Array {
+  return strToU8(text)
+}
+
+export function isZipArchive(bytes: Uint8Array): boolean {
+  return bytes.length >= 4 && bytes[0] === 0x50 && bytes[1] === 0x4b
+}