chore: add docker release workflows for Zeabur deployment

[ThaddeusJiang]

Summary

• add typelens-style reusable Docker publish workflow for GHCR
• add release workflows for published releases and manual prerelease creation
• switch the Zeabur template bot service to PREBUILT_V2 using the published image
• add a local mise run confirm-docker-build verification task and document the image tag

Validation

• ruby -e 'require "yaml"; Dir[".github/workflows/*.yml"].each { |f| YAML.load_file(f); puts "OK #{f}" }'
• git diff --check
• docker compose config
• mise run confirm-docker-build