feat(mcp): automation tools — playbooks, runs, schedules, alert actions, docker prune

MCP-6 #4970 "Automation tools: playbooks, runs, schedules, alert actions".

Viewer: list_playbooks, get_playbook (secret defaults masked), list_inventory
(variable names only), list_ansible_runs, get_ansible_run (log tail + grep),
list_schedules, wait_for_run (polls, 120s cap).

Operator: run_playbook (check mode unless check=false; a steward:confirm
playbook applies only with confirmed=true; secret variables reach the run
but are never stored, audited or returned), cancel_ansible_run, and
create/update/delete_schedule (secrets refused, check by default).

Admin: set_alert_action, and the docker plugin's prune_docker, which
previews from the disk report unless check=false (Ansible's check mode
skips the prune commands, so a check run would show nothing).

Every write is audited as "<user> via MCP" with the token id; the audit
tool's user filter includes those rows. prune_extra_vars moves to the
docker service so the page and the tool share it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/docker/routes.py

@@ -31,17 +31,6 @@ def _error(status: int, code: str, detail: str | None = None):
     return jsonify(body), status
 
 
-def _prune_extra_vars(prune_target: str) -> dict:
-    """Extra-vars for the bundled docker_prune playbook. "Prune unused images"
-    means ALL unused (docker image prune -a), not just dangling; the full system
-    prune stays conservative (-f, no -a) per the operator's choice (m78). Pure
-    helper so the mapping is unit-tested without the request/DB stack."""
-    extra_vars: dict = {"prune_target": prune_target}
-    if prune_target == "images":
-        extra_vars["prune_all_images"] = True
-    return extra_vars
-
-
 def _human_bytes(n: int | None) -> str:
     """Compact binary size string (e.g. '1.4 GiB', '512 MiB', '0 B')."""
     if n is None:
@@ -544,7 +533,7 @@ async def disk_prune(host_id: str):
 
     form = await request.form
     prune_target = (form.get("target", "") or "").strip()
-    if prune_target not in ("containers", "images", "system"):
+    if prune_target not in docker_svc.PRUNE_TARGETS:
         return _error(400, "bad_target", "Unknown prune target")
 
     async with current_app.db_sessionmaker() as db:
@@ -556,7 +545,7 @@ async def disk_prune(host_id: str):
                       "Link an Ansible target to this host before pruning")
 
     # extra_vars_map outranks the playbook's own `vars:` defaults.
-    extra_vars = _prune_extra_vars(prune_target)
+    extra_vars = docker_svc.prune_extra_vars(prune_target)
 
     actor_role = UserRole(session.get("user_role", "viewer"))
     run, _source, err = await invoke_capability(