feat: expose interLink server version via API

[w3lld1]

Summary

I added a GET /version endpoint so operators can query the version of the running interLink server without shell access. The response uses the same build-time version value already shown by the CLI and startup logs:

{"version":"0.6.2"}

I also return 405 Method Not Allowed with Allow: GET for other methods.

Validation

• go test -p 1 ./pkg/interlink/api ./cmd/interlink -count=1
• go vet ./pkg/interlink/api ./cmd/interlink
• git diff --check origin/main...HEAD

I did not run the K3s end-to-end suite locally because it requires a full cluster environment; the focused handler and server-package checks cover this change.

Fixes #544

[netlify]

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[dciangot]

Thank you @w3lld1 ! I have just a comment about what is more useful to have as an information returned from this endpoint

[dciangot]

I'd rather put the running interLink software version, in place of the kubelet.

[w3lld1]

Thanks — updated the endpoint in 64cff911 to return the running interLink server version instead of the virtual kubelet version. The e2e and other project checks pass. The remaining lint failure is a toolchain issue: CI selects Go 1.27, while golangci-lint v2.11.2 was built with Go 1.26 and panics before reporting any source finding.