Implement structured logging with slog

- Replace zerolog with Go's standard slog package
- Add ColorHandler for terminal color output
- Add context-aware logging system
- Format attributes on the same line as log messages
- Use green color for INFO level logs
- Set up context value extraction helpers

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

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

common/contextlog/contextlog.go

@@ -0,0 +1,112 @@
+package contextlog
+
+import (
+	"context"
+	"fmt"
+	"log/slog"
+
+	"gemini-grc/contextutil"
+)
+
+// SlogEventWithContext adds context information as structured fields to the log event.
+func SlogEventWithContext(ctx context.Context, logger *slog.Logger) *slog.Logger {
+	// Start with the provided logger
+	if logger == nil {
+		// If logger isn't initialized, use the default logger
+		return slog.Default()
+	}
+
+	// Get context values - will be added directly to log records
+	host := contextutil.GetHostFromContext(ctx)
+	requestID := contextutil.GetRequestIDFromContext(ctx)
+	component := contextutil.GetComponentFromContext(ctx)
+	workerID := contextutil.GetWorkerIDFromContext(ctx)
+	url := contextutil.GetURLFromContext(ctx)
+
+	// Add all context fields to the logger
+	if host != "" {
+		logger = logger.With("host", host)
+	}
+
+	if requestID != "" {
+		logger = logger.With("request_id", requestID)
+	}
+
+	if workerID >= 0 {
+		logger = logger.With("worker_id", workerID)
+	}
+
+	if component != "" {
+		logger = logger.With("component", component)
+	}
+
+	if url != "" {
+		logger = logger.With("url", url)
+	}
+
+	return logger
+}
+
+// LogDebugWithContext logs a debug message with context information.
+func LogDebugWithContext(ctx context.Context, logger *slog.Logger, format string, args ...interface{}) {
+	if logger == nil {
+		return
+	}
+
+	// Create logger with context fields
+	contextLogger := SlogEventWithContext(ctx, logger)
+
+	// Format the message
+	message := fmt.Sprintf(format, args...)
+
+	// Log with context data in the record attributes
+	contextLogger.Debug(message)
+}
+
+// LogInfoWithContext logs an info message with context information.
+func LogInfoWithContext(ctx context.Context, logger *slog.Logger, format string, args ...interface{}) {
+	if logger == nil {
+		return
+	}
+
+	// Create logger with context fields
+	contextLogger := SlogEventWithContext(ctx, logger)
+
+	// Format the message
+	message := fmt.Sprintf(format, args...)
+
+	// Log with context data in the record attributes
+	contextLogger.Info(message)
+}
+
+// LogWarnWithContext logs a warning message with context information.
+func LogWarnWithContext(ctx context.Context, logger *slog.Logger, format string, args ...interface{}) {
+	if logger == nil {
+		return
+	}
+
+	// Create logger with context fields
+	contextLogger := SlogEventWithContext(ctx, logger)
+
+	// Format the message
+	message := fmt.Sprintf(format, args...)
+
+	// Log with context data in the record attributes
+	contextLogger.Warn(message)
+}
+
+// LogErrorWithContext logs an error message with context information
+func LogErrorWithContext(ctx context.Context, logger *slog.Logger, format string, args ...interface{}) {
+	if logger == nil {
+		return
+	}
+
+	// Create logger with context fields
+	contextLogger := SlogEventWithContext(ctx, logger)
+
+	// Format the message
+	msg := fmt.Sprintf(format, args...)
+
+	// Log with context data in the record attributes
+	contextLogger.Error(msg, slog.String("error", msg))
+}