[logging] Add FileLogSink, CompositeLogSink, and SHARPEMU_LOG_FILE env support (#50)

- FileLogSink: thread-safe file writer with AutoFlush, FileShare.Read for
  concurrent read access (tail -f), automatic parent directory creation,
  full date-time timestamps, IDisposable for graceful shutdown
- CompositeLogSink: fan-out to multiple sinks with per-sink exception
  isolation (one broken sink cannot silence the others), IDisposable
  propagates to children
- SharpEmuLog: ResolveSinkFromEnvironment() reads SHARPEMU_LOG_FILE and
  creates CompositeLogSink(console + file) when set; Sink setter now
  disposes the previous IDisposable sink to prevent file handle leaks;
  Shutdown() flushes and disposes the active sink
- Program.cs: Main wrapped in try/finally to guarantee SharpEmuLog.Shutdown()
  runs on all exit paths (GUI, mitigated child, normal, exception)

Co-authored-by: Hermes Atlas <hermesatlas@example.com>

src/SharpEmu.CLI/Program.cs

@@ -36,6 +36,18 @@ internal static partial class Program
 
     [STAThread]
     private static int Main(string[] args)
+    {
+        try
+        {
+            return Run(args);
+        }
+        finally
+        {
+            SharpEmuLog.Shutdown();
+        }
+    }
+
+    private static int Run(string[] args)
     {
         args = NormalizeInternalArguments(args, out var isMitigatedChild);
         if (args.Length == 0 && !isMitigatedChild)
@@ -66,7 +78,7 @@ internal static partial class Program
 
         ebootPath = Path.GetFullPath(ebootPath);
         Console.Error.WriteLine($"[DEBUG] Full path: {ebootPath}");
-        
+
         if (!File.Exists(ebootPath))
         {
             Log.Error($"EBOOT file was not found: {ebootPath}");