Keep Go 1.26.5 and make lint workflows toolchain-consistent

[Copilot]

This PR keeps the repository on the newest Go version and resolves pipeline breakage caused by lint jobs running a golangci-lint binary built with an older Go toolchain. It also removes reliance on a flaky remote config fetch path in the legacy lint action.

• Go version baseline

  • go.mod stays on go 1.26.5.
  • release-assets workflow stays aligned with actions/setup-go@v5 using go-version: '1.26.5'.

• Lint pipeline hardening (docker workflows)

  • Replaced golangci/golangci-lint-action@v2 usage in:
    • ci-docker.yaml
    • release-docker.yaml
    • scheduled-docker.yaml
  • New lint path:
    1. set up Go 1.26.5
    2. install lint binary via go install
    3. run golangci-lint directly

• Why this fixes the issue

  • Ensures lint binary/toolchain matches the repository Go target (1.26.5), avoiding version mismatch failures in CI.

- uses: actions/setup-go@v5
  with:
    go-version: '1.26.5'
    check-latest: true

- name: Install golangci-lint
  run: go install github.com/golangci/golangci-lint/cmd/golangci-lint@latest

- name: Run golangci-lint
  run: golangci-lint run --print-resources-usage