540 sftp does not download the file then errors

[Hirogen]

This pull request includes several improvements and fixes across the codebase. The main changes focus on improving robustness for file handling (especially with SFTP and plugin-based filesystems), updating localization resources, and modernizing versioning and build configuration. Additionally, a new test class ensures correct behavior when file system plugins return null, preventing possible exceptions.

File handling robustness and SFTP improvements: #540

• Added null checks and exception handling in RolloverFilenameHandler.GetNameList and SftpLogFileInfo to prevent crashes when plugins or SFTP operations fail (e.g., when files do not exist or permissions are denied). This includes returning false if a plugin or file info is missing, and logging errors for SFTP exceptions. [1] [2] [3]
• Introduced a new test class RolloverFilenameHandlerNullTests to verify that GetNameList does not throw exceptions in edge cases, such as when plugins return null or when rollover files are missing.

Localization and resource updates: #544

• Updated English, German, and Chinese resource files to correct and clarify messages related to portable mode activation, migration, and user prompts. This includes swapping and fixing resource values for better clarity and accuracy. [1] [2] [3] [4] [5] [6] [7]

Build and versioning modernization: #542

• Updated project version numbers from 1.21.0.0 to 1.31.0.0 in Directory.Build.props, and improved assembly info generation settings. Also updated company name and release notes URL. [1] [2]
• Modernized the installer script to allow AppVersion to be passed via the command line or read from the built executable, aligning with automated build systems. [1] [2]
• Removed hardcoded assembly version attributes from AssemblyInfo.cs in favor of project file configuration.

Minor code quality and bug fixes:

• Fixed a potential null reference in LogWindow.GetPersistenceData by checking if _logFileReader is not null before accessing its properties.
• Minor formatting and code style adjustments, such as using discard assignments and clarifying TODOs for future improvements. [1] [2] [3] [4]

These changes collectively improve the stability, maintainability, and user experience of the application.