Security: file name restriction

[Ludy87]

Description of Changes

This PR updates the check_properties.yml workflow to refine the file-matching regex for properties files.

What was changed:

• Modified the regex used in two locations:
  1. In the GitHub CLI (gh) command to filter changed files:

     - '^src/main/resources/messages_[a-zA-Z_]+\.properties$'
     + '^src/main/resources/messages_[a-zA-Z_]{2}_[a-zA-Z_]{2,7}\.properties$'

  2. In the code to match relevant property files:

     - /^src\/main\/resources\/messages_[a-zA-Z_]+\.properties$/
     + /^src\/main\/resources\/messages_[a-zA-Z_]{2}_[a-zA-Z_]{2,7}\.properties$/

Why the change was made:

• The previous regex matched any property files with loosely defined patterns, including invalid or unintended formats.
• The updated regex ensures stricter matching of valid locale patterns:
  • Locale codes in the format xx_XX where:
    • xx represents a 2-character language code.
    • XX represents a 2-7 character region code.

Challenges encountered:

• Ensuring compatibility across both the GitHub CLI command.
• Avoiding edge cases where valid property files might be excluded unintentionally.

Closes # (issue_number)

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Checklist

General

• I have read the Contribution Guidelines
• I have read the Stirling-PDF Developer Guide (if applicable)
• I have read the How to add new languages to Stirling-PDF (if applicable)
• I have performed a self-review of my own code
• My changes generate no new warnings

Documentation

• I have updated relevant docs on Stirling-PDF's doc repo (if functionality has heavily changed)
• I have read the section Add New Translation Tags (for new translation tags only)

UI Changes (if applicable)

• Screenshots or videos demonstrating the UI changes are attached (e.g., as comments or direct attachments in the PR)

Testing (if applicable)

• I have tested my changes locally. Refer to the Testing Guide for more details.