Following the work done with VisualEditor and CampaignEvents, add a new extension to mediawiki-catalyst-daily.yaml that builds a catalyst env for the Echo extension, runs its selenium tests, tears down, and reports results. Cron: 15 8 * * *.

AC:

• New Echo entry added under the extension: matrix in jjb/mediawiki-catalyst-daily.yaml
• Required extensions/skins for Echo's selenium tests identified and included in json-values
• Job runs end-to-end at least once (env build → selenium → teardown) with tests green