ci: disable Dependabot version updates

[imneov]

What type of PR is this?

• CI / tooling

What this PR does and why

Removes the Dependabot version-update configuration added during open-source readiness. Scheduled dependency, Docker image and GitHub Actions upgrade PRs will stop after this PR is merged. Existing Dependabot PRs remain open for maintainers to handle separately. The repository setting for Dependabot security updates is independent.

Which issue(s) this PR fixes

None. This is a requested rollback of the version-update configuration.

How it was tested

The diff deletes only .github/dependabot.yml. git diff --check passed. No application tests were run because application code did not change.

Checks

• go test ./... and gofmt -l . is empty (not run; Go code unchanged)
• npm run typecheck && npm test && npm run build in web/ (not run; web/ unchanged)
• helm lint --strict helm/console (not run; chart unchanged)
• No internal hostnames, IPs, registries or credentials added

Notes for reviewers

Version-update PRs may continue until this PR is merged. Existing bot PRs are not closed by this change.

Release note

None