Test: Improve Temporary File Cleanup and Path Management

[nickna]

Description

Standardize temporary file creation, cleanup, and path management across all tests to prevent test artifacts and improve reliability.

Phase

Phase 0: Test Technical Debt Cleanup

Epic

Related to #202

Acceptance Criteria

• Audit all tests that create temporary files or directories
• Create standardized TestFileManager utility
• Ensure all temporary files are cleaned up in TearDown methods
• Use unique paths to prevent test interference
• Add failure cleanup for interrupted tests

Current Issues

• Some tests use hardcoded temporary paths
• Inconsistent cleanup of failed test artifacts
• Potential file conflicts between parallel tests

Proposed Solution

public class TestFileManager : IDisposable
{
    private readonly List<string> _tempPaths = new();
    
    public string CreateTempDirectory(string prefix = "test")
    {
        var path = Path.Combine(Path.GetTempPath(), $"{prefix}_{Guid.NewGuid():N}");
        Directory.CreateDirectory(path);
        _tempPaths.Add(path);
        return path;
    }
    
    public string CreateTempFile(string extension = ".tmp")
    {
        var path = Path.Combine(Path.GetTempPath(), $"test_{Guid.NewGuid():N}{extension}");
        _tempPaths.Add(path);
        return path;
    }
    
    public void Dispose()
    {
        foreach (var path in _tempPaths)
        {
            try
            {
                if (Directory.Exists(path))
                    Directory.Delete(path, true);
                else if (File.Exists(path))
                    File.Delete(path);
            }
            catch { /* Ignore cleanup failures */ }
        }
    }
}

Files to Review

• Search for Path.GetTempPath() usage
• Tests creating database files
• Serialization tests
• Integration tests with file I/O