refactor: full-stack restructure with multi-tenancy, workspace management, and K8s diagnostics

- Add Workspace domain (entity, repository, service, handler, DTO)
- Add multi-tenant K8s client with tenant binding and quota management
- Add K8s diagnostics client (instance diagnostics)
- Add authorization middleware (authz package)
- Restructure frontend to feature-based architecture (features/)
- Add User Management page in configuration
- Add AccessDenied page and route guards
- Refactor shared components (form inputs, layout, UI)
- Update Tailwind config for new design system
- Add comprehensive documentation (docs/, tasks/, plans)
- Improve cluster service with better kubeconfig handling
- Add tests for crypto, config, helm client, tenant binding

backend/internal/domain/service/quota_quantity.go

@@ -0,0 +1,54 @@
+package service
+
+import (
+	"strconv"
+	"strings"
+
+	"github.com/ocdp/cluster-service/internal/domain/entity"
+)
+
+func normalizeStandardQuotaQuantity(value string) string {
+	value = strings.TrimSpace(value)
+	upper := strings.ToUpper(value)
+	switch {
+	case strings.HasSuffix(upper, "MB"):
+		return strings.TrimSpace(value[:len(value)-2]) + "M"
+	case strings.HasSuffix(upper, "GB"):
+		return strings.TrimSpace(value[:len(value)-2]) + "G"
+	default:
+		return value
+	}
+}
+
+func normalizeGPUMemoryQuota(value string) (string, error) {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return "", nil
+	}
+	upper := strings.ToUpper(value)
+	multiplier := int64(1)
+	number := value
+	switch {
+	case strings.HasSuffix(upper, "MB"):
+		number = strings.TrimSpace(value[:len(value)-2])
+	case strings.HasSuffix(upper, "M"):
+		number = strings.TrimSpace(value[:len(value)-1])
+	case strings.HasSuffix(upper, "GB"):
+		number = strings.TrimSpace(value[:len(value)-2])
+		multiplier = 1000
+	case strings.HasSuffix(upper, "G"):
+		number = strings.TrimSpace(value[:len(value)-1])
+		multiplier = 1000
+	case strings.HasSuffix(upper, "GIB"):
+		number = strings.TrimSpace(value[:len(value)-3])
+		multiplier = 1024
+	case strings.HasSuffix(upper, "GI"):
+		number = strings.TrimSpace(value[:len(value)-2])
+		multiplier = 1024
+	}
+	parsed, err := strconv.ParseInt(number, 10, 64)
+	if err != nil || parsed < 0 {
+		return "", entity.ErrInvalidTenantResourceQuota
+	}
+	return strconv.FormatInt(parsed*multiplier, 10), nil
+}