refactor(prepare): replace bash-over-SSH with Ansible playbook

- Replace 776-line manual SSH implementation with a declarative
  Ansible playbook embedded in the binary via go:embed
- Add ensureAnsible() to auto-detect and install ansible-playbook
  (pipx → apt-get → dnf/yum → pip --break-system-packages)
- Fix deployment server resolution to match by host IP as well as name
- Fix Caddy yum service tasks to skip when Caddy already installed
- Add nextdeployd pre-check to suppress daemon 404 noise on re-runs
- Drop StreamWriter, remoteExec, isFunctional, isInstalled and all
  per-distro install functions (~600 lines removed)

Author: aynaash