Deploy actions: no branch or environment deployment support

Feature description

The actions have no prefixing, no deploy-with-triggers-disabled, and no namespace or resource mapping. namespace (force a single target) is the only scoping input; kestractl flows deploy also has --recursive and --fail-fast, neither exposed.

An existing customer's per-PR staging workflow therefore does regex surgery on the flow YAML before upload: prefix namespaces with staging.pr<N>, flip system.readOnly, inject disabled: true under every trigger, then upload.

Open question:
Does this belong in the action at all? io.kestra.plugin.git.SyncFlows already does branch → targetNamespace with namespace rewriting, scoped delete and a dryRun diff, but it is a pull model running inside Kestra, not a push from CI.

For a proper push-from-CI workflow, the action needs at least a namespace prefix or mapping input and a triggers-disabled deploy.