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/config/config.go

@@ -2,7 +2,6 @@ package config
 
 import (
 	"fmt"
-	"log/slog"
 	"os"
 	"reflect"
 	"strconv"
@@ -14,8 +13,13 @@ import (
 
 // Config holds the application configuration.
 type Config struct {
-	LogLevel string       `yaml:"log_level"`
-	Server   ServerConfig `yaml:"server"`
+	Logging LoggingConfig `yaml:"logging"`
+	Server  ServerConfig  `yaml:"server"`
+}
+
+// LoggingConfig holds logging-specific configuration.
+type LoggingConfig struct {
+	Level string `yaml:"level"`
 }
 
 // ServerConfig holds server-specific configuration.
@@ -50,22 +54,6 @@ func Load(configPath string, envPrefix string) (*Config, error) {
 	return cfg, nil
 }
 
-// ParseLogLevel converts a string log level to a slog.Level.
-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
-	}
-}
-
 // overrideFromEnv uses reflection to traverse the struct and update fields from env vars.
 func overrideFromEnv(cfg interface{}, prefix string) error {
 	v := reflect.ValueOf(cfg)