chore: Modulname github.com/archivmail → archivmail

Go-Modul in go.mod und allen 45 Go-Dateien umbenannt.

internal/api/quota_handlers.go

@@ -6,9 +6,9 @@ import (
 	"net/http"
 	"strconv"
 
-	"github.com/archivmail/internal/audit"
-	"github.com/archivmail/internal/storage"
-	"github.com/archivmail/internal/tenantstore"
+	"archivmail/internal/audit"
+	"archivmail/internal/storage"
+	"archivmail/internal/tenantstore"
 )
 
 // handleGetTenantUsage returns current quota config and usage for a tenant.