Add validation to fileinfo plugin input pattern

CMK-12283

Change-Id: Icae251a5110fb52eb07f571dcb9b45a125993a6a

Author: ramadanKhalifa

.werks/18352.md

@@ -0,0 +1,35 @@
+[//]: # (werk v2)
+# fileinfo: Validate file group patterns to prevent configuration errors
+
+key        | value
+---------- | ---
+date       | 2025-07-22T13:39:35+00:00
+version    | 2.5.0b1
+class      | fix
+edition    | cee
+component  | checks
+level      | 1
+compatible | no
+
+### Problem
+Previously, invalid regular expressions in file group patterns (in the fileinfo check) could be saved without warning.
+This could lead to runtime errors.
+
+### Fix
+Patterns are now validated when editing the rule.
+Only valid regular expressions can be saved.
+
+### Impact
+If your existing configuration contains invalid patterns, you will see an error message like:
+```
+The pattern <pattern> is not a valid regular expression: <error message>
+```
+
+You can either:
+
+- Fix the broken patterns immediately as prompted, or
+- Skip fixing and proceed with the update — your configuration will still work as before, but
+editing those rules later will cause invalid patterns to be lost (the rule will be emptied).
+
+### Action Required
+Review and correct any problematic patterns before applying changes to the configuration.