feat: implement comprehensive configuration validation and integrate into store loading and server initialization.

cmd/ds2api/main.go

@@ -24,7 +24,11 @@ func main() {
 	config.RefreshLogger()
 	webui.EnsureBuiltOnStartup()
 	_ = auth.AdminKey()
-	app := server.NewApp()
+	app, err := server.NewApp()
+	if err != nil {
+		config.Logger.Error("server initialization failed", "error", err)
+		os.Exit(1)
+	}
 	port := strings.TrimSpace(os.Getenv("PORT"))
 	if port == "" {
 		port = "5001"