🧹 Refactor duplicated hardcoded cryptographic keys

[LDzik]

🎯 What

Extracted hardcoded cryptographic strings (data, key, iv) into private constants within the MyTile class in LWCredentialProvider/CredentialProvider.cs.

💡 Why

This improves maintainability and readability by removing code duplication and providing a single source of truth for these values.

✅ Verification

• Manually verified the changes in LWCredentialProvider/CredentialProvider.cs.
• Conducted a code review which confirmed the refactoring is safe and preserves existing functionality.
• Attempted to run dotnet build, but was hindered by environment-specific timeouts during the restore process.

✨ Result

Improved code health and maintainability by centralizing configuration values.

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PR created automatically by Jules for task 10611772927724722315 started by @LDzik

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