refactor(logging): move logging setup to internal/logging

Moves logging configuration and setup to a dedicated package. Updates Config struct to use nested LoggingConfig. Updates main.go to use the new logging package.

internal/logging/logging.go

@@ -0,0 +1,37 @@
+package logging
+
+import (
+	"log/slog"
+	"os"
+	"strings"
+)
+
+// Config holds the logging configuration.
+type Config struct {
+	Level string `yaml:"level"`
+}
+
+// Configure sets up the global logger based on the provided configuration.
+func Configure(cfg Config) *slog.Logger {
+	opts := &slog.HandlerOptions{
+		Level: parseLogLevel(cfg.Level),
+	}
+	logger := slog.New(slog.NewJSONHandler(os.Stdout, opts))
+	slog.SetDefault(logger)
+	return logger
+}
+
+func parseLogLevel(level string) slog.Level {
+	switch strings.ToLower(level) {
+	case "debug":
+		return slog.LevelDebug
+	case "info":
+		return slog.LevelInfo
+	case "warn":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		return slog.LevelInfo
+	}
+}