improvement(service): replace duplicate checkForProjectNamespace methods with util.CheckForProjectNamespace

[mdryaan]

Description

Three service structs (ClusterService, SliceConfigService, SliceQoSConfigService) each defined a private checkForProjectNamespace(*corev1.Namespace) bool method with an identical body. The same check already exists as the public util.CheckForProjectNamespace in util/reconciliation_utility.go. All three private methods were removed and their single call sites updated to call util.CheckForProjectNamespace directly. The fmt import in slice_qos_config_service.go was also removed as it was only used by the deleted method. Net change: −19 lines, no behaviour change.

Fixes #384

How Has This Been Tested?

Removed checkForProjectNamespace from cluster_service.go:337–339, slice_config_service.go:245–247, and slice_qos_config_service.go:127–129. Updated call sites at cluster_service.go:75, slice_config_service.go:131, and slice_qos_config_service.go:113 to call util.CheckForProjectNamespace. Removed unused fmt import from slice_qos_config_service.go. go build ./... passes. Pre-existing make vet failure (undefined: util.Client in access_control_service_test.go) exists on master before this branch and is unrelated to this change.

Checklist:

• The title of the PR states what changed and the related issues number (used for the release note).
• Does this PR requires documentation updates? — No.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas. — N/A.
• I have tested it for all user roles. — N/A.
• I have added all the required unit test cases.

Does this PR introduce a breaking change for other components like worker-operator?

No

Remove duplicate checkForProjectNamespace private methods from ClusterService, SliceConfigService, and SliceQoSConfigService; use shared  util.CheckForProjectNamespace instead