Add push deploy controls and status webapp actions

[moritzbrantner]

Summary

• Adds per-site push deploy controls and broader admin actions in the status webapp.
• Moves the supported dashboard to monitor/webapp and adds API support for site settings and nginx controls.
• Consolidates deploy/runtime state handling around host-local JSON state files and removes the legacy Python dashboard path.
• Updates server preparation and service management entrypoints to direct Python commands, with nginx enabled during setup.
• Replaces the old deploy CI workflow with a single repository-wide test workflow and updates docs and examples accordingly.

Testing

• Ran repository validation via ./tests/run-tests.sh in CI workflow.
• Added/updated unit coverage for deploy engine, server prep, hardening, setup scripts, and status webapp controls.
• Added frontend test coverage for the status webapp control flows.
• Not run locally in this environment.