fix(packaging): verify bundled startup dependencies

cmshopee.spec

@@ -7,11 +7,21 @@ include config files, SQLite databases, Chrome profiles, generated images,
 logs, prompts, or other operator data.
 """
 
+import importlib.util
 import os
 
 from PyInstaller.utils.hooks import collect_data_files
 
 block_cipher = None
+try:
+    backports_tarfile_spec = importlib.util.find_spec("backports.tarfile")
+except ModuleNotFoundError:
+    backports_tarfile_spec = None
+if backports_tarfile_spec is None:
+    raise SystemExit(
+        "Missing backports.tarfile. Run: "
+        "py -3.10 -m pip install -r requirements-build.txt"
+    )
 default_prompt_datas = collect_data_files(
     "app.default_prompts",
     includes=["**/*.txt"],
@@ -36,6 +46,7 @@ a = Analysis(
         "PySide6.QtCore",
         "PySide6.QtGui",
         "PySide6.QtWidgets",
+        "backports.tarfile",
     ],
     hookspath=[],
     hooksconfig={},