refactor: complete conversion of log calls to slog (#787)

backend/internal/common/env_config.go

@@ -3,8 +3,9 @@ package common
 import (
 	"errors"
 	"fmt"
-	"log"
+	"log/slog"
 	"net/url"
+	"os"
 
 	"github.com/caarlos0/env/v11"
 	_ "github.com/joho/godotenv/autoload"
@@ -57,7 +58,8 @@ var EnvConfig = defaultConfig()
 func init() {
 	err := parseEnvConfig()
 	if err != nil {
-		log.Fatalf("Configuration error: %v", err)
+		slog.Error("Configuration error", slog.Any("error", err))
+		os.Exit(1)
 	}
 }