chore: bump version to v2026.4.311 and add footer clear fix}
- Bump version from v2026.4.310 to v2026.4.311 across all docs and artifacts
- Bump package.json version to v2026.4.312 and update nodejs to v24.14.1
- Add changelog entry for v2026.4.311: guard against missing submodule config
- Add `clear:both` div before footer in footer.twig to fix layout float issues