Develop an input package for the Docker stats receiver that's installable + configurable via Fleet and can be deployed to Hybrid Agent.

Receiver Documentation

https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/receiver/dockerstatsreceiver

Definition of Done

• Published to epr.elastic.co as tech preview
• Installs via Kibana UI and Fleet API
• Deploys to Agent + starts collector running receiver
• Ingests sample data to otel.docker stats-* datastream
• Mapping matches OTel-native format (spec)
• Content pack auto-installs (if exists)
• elastic-package test passes
• Manual smoke test documented in PR
• README includes purpose, sample config, troubleshooting steps, relevant links
• GitHub Codeowner is @elastic/ecosystem
• Optional review from team owning ECS equivalent
• Table in parent issue is updated with PR link and anything else of note