Replace iOSbackup with iphone_backup_decrypt

Replace the unmaintained iOSbackup dependency with iphone_backup_decrypt
(MIT licensed, actively maintained). This fixes file corruption caused by
iOSbackup truncating files to inaccurate sizes from backup metadata.

The extract-key command and --key-file option are preserved via an
MVTEncryptedBackup subclass that patches the keybag unlock to
capture/reuse the derived PBKDF2 key.

Closes #669

pyproject.toml

@@ -24,7 +24,8 @@ dependencies = [
     "simplejson==3.20.2",
     "packaging==26.0",
     "appdirs==1.4.4",
-    "iOSbackup==0.9.925",
+    "iphone_backup_decrypt==0.9.0",
+    "pycryptodome>=3.18",
     "adb-shell[usb]==0.4.4",
     "libusb1==3.3.1",
     "cryptography==46.0.6",