fix: replace module-name regex with str.isidentifier per-segment

Semgrep flagged the compiled regex as a potential ReDoS pattern.
Validating each dotted segment with str.isidentifier gives the
same guarantee against shell/path payloads without any regex,
removing the heuristic warning and reading more directly.

Author: JE-Chen

je_mail_thunder/utils/package_manager/package_manager_class.py

@@ -1,15 +1,14 @@
-import re
 from importlib import import_module
 from importlib.util import find_spec
 from inspect import getmembers, isfunction, isbuiltin, isclass
 
 from je_mail_thunder.utils.logging.loggin_instance import mail_thunder_logger
 
-_MODULE_NAME_PATTERN = re.compile(r"^[A-Za-z_][A-Za-z0-9_]*(\.[A-Za-z_][A-Za-z0-9_]*)*$")
-
 
 def _is_safe_module_name(package: str) -> bool:
-    return isinstance(package, str) and bool(_MODULE_NAME_PATTERN.fullmatch(package))
+    if not isinstance(package, str) or not package:
+        return False
+    return all(part.isidentifier() for part in package.split("."))
 
 
 class PackageManager: