iot2050-firmware-update: Improve min_version calculation in backup

Refactor the firmware update script to more robustly calculate the
`min_version` during the backup process.

The previous implementation was brittle, as it incorrectly assumed the
version prefix was always a single character. This caused failures with
version strings that did not have a prefix (e.g., "1.6.2").

This change introduces a new `_get_min_version` helper method that uses
a regular expression to parse the version string. It correctly
identifies numeric components and replaces any number greater than 1
with a '1', while preserving the original zero-padding.

The logic now first isolates the main version tag (the portion before
any hyphen) and then passes it to the new helper method to ensure a
correct and reliable `min_version` is generated for the backup
configuration.

Signed-off-by: Li Hua Qian <huaqian.li@siemens.com>

Author: huaqianli

meta-example/recipes-app/iot2050-firmware-update/files/iot2050-firmware-update.tmpl

@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (c) Siemens AG, 2020-2024
+# Copyright (c) Siemens AG, 2020-2026
 #
 # Authors:
 #  Chao Zeng <chao.zeng@siemens.com>
@@ -122,6 +122,7 @@ from io import StringIO
 from progress.bar import Bar
 from threading import Thread, Event
 from types import SimpleNamespace as Namespace
+import re
 
 class ErrorCode(Enum):
     """The ErrorCode class describes the return codes"""
@@ -489,6 +490,20 @@ class FirmwareUpdate():
         except UpgradeError as e:
             raise UpgradeError(e.err, e.code)
 
+    def _get_min_version(self, version_str):
+        """Calculate the minimal version from a version string component."""
+        parts = re.split(r'(\d+)', version_str)
+        result = []
+        for part in parts:
+            if part.isdigit():
+                if int(part) > 1:
+                    result.append('1'.zfill(len(part)))
+                else:
+                    result.append(part)
+            else:
+                result.append(part)
+        return "".join(result)
+
     def backup(self):
         """Backup the original firmware from flash"""
         print("\nFirmware backup started")
@@ -521,10 +536,10 @@ class FirmwareUpdate():
                             if "BUILD_ID" in key:
                                 break
                         target_board = model_f.read().replace("\u0000", "")
+                    version_tag = value.replace('"', '').split('-')[0]
                     tmpl_json['firmware'][0]['target_boards'] = target_board
                     tmpl_json['target_os'][0]['min_version'] = \
-                        value.replace('"', '')[:1] + \
-                        tmpl_json['target_os'][0]['min_version'][1:]
+                        self._get_min_version(version_tag)
                     file_content = bytes(json.dumps(tmpl_json, indent=4), "utf8")
                 else:
                     raise UpgradeError("Wrong Firmware Type!")