fix: CVE-2025-61729 & CVE-2025-61726 - upgrade go version to >1.25.5

[infernus01]

Changes

Scope of this fix is to address CVE-2025-61729 & CVE-2025-61726 by upgrading go version above 1.25.5, and cosign/sigstore version to 2.6.2.

/kind bug

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• Includes tests (if functionality changed/added)
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[divyansh42]

/ok-to-test

[infernus01]

closed in favour of #2750