[CI] Add version field to golangci-lint configuration

[Copilot]

Description

golangci-lint v2.0+ requires an explicit version field in the configuration. The missing field caused CI failures:

Error: can't load config: unsupported version of the configuration: ""

Added version: 2 to .golangci.yml to comply with the v2 configuration format.

Notes for Reviewers

Single line change to configuration file. No functional changes to linting rules or behavior.

Signed commits

• Yes, I signed my commits.

Original prompt

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This section details on the original issue you should resolve

<issue_title>[CI] Upgrade golangci-lint configuration</issue_title>
<issue_description>#### Current Behavior

golangci-lint run ./...
Error: can't load config: unsupported version of the configuration: "" See https://golangci-lint.run/docs/product/migration-guide for migration instructions
The command is terminated due to an error: can't load config: unsupported version of the configuration: "" See https://golangci-lint.run/docs/product/migration-guide for migration instructions
make: *** [lint] Error 3

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  </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [CI] Upgrade golangci-lint configuration #500

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