debug(logger): add AtomicLevel tracking to diagnose level changes

Added debug output to track:
1. AtomicLevel value when created
2. AtomicLevel value after Build()
3. Log.Level() value after Build()

This will help identify if Build() or something else is changing the level.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

backend/mpc-system/pkg/logger/logger.go

@@ -38,8 +38,11 @@ func Init(cfg *Config) error {
 		outputPath = cfg.OutputPath
 	}
 
+	atomicLevel := zap.NewAtomicLevelAt(level)
+	println("DEBUG: Created AtomicLevel:", atomicLevel.String())
+
 	zapConfig := zap.Config{
-		Level:             zap.NewAtomicLevelAt(level),
+		Level:             atomicLevel,
 		Development:       false,
 		DisableCaller:     false,
 		DisableStacktrace: false,
@@ -69,6 +72,9 @@ func Init(cfg *Config) error {
 		return err
 	}
 
+	println("DEBUG: After Build, AtomicLevel:", atomicLevel.String())
+	println("DEBUG: After Build, Log.Level():", Log.Level().String())
+
 	Sugar = Log.Sugar()
 
 	// Replace global zap logger to ensure our config takes effect