refactor(swarm): one file per endpoint, matching existing router layout

Splits the three grouped router files into eight api_<verb>_<resource>.py
modules under decnet/web/router/swarm/ to match the convention used by
router/fleet/ and router/config/. Shared request/response models live in
_schemas.py. Keeps each endpoint easy to locate and modify without
stepping on siblings.

decnet/web/router/swarm/api_teardown_swarm.py

@@ -0,0 +1,51 @@
+"""POST /swarm/teardown — tear down one or all enrolled workers."""
+from __future__ import annotations
+
+import asyncio
+from typing import Any
+
+from fastapi import APIRouter, Depends, HTTPException
+
+from decnet.logging import get_logger
+from decnet.swarm.client import AgentClient
+from decnet.web.db.repository import BaseRepository
+from decnet.web.dependencies import get_repo
+from decnet.web.router.swarm._schemas import (
+    DeployResponse,
+    HostResult,
+    TeardownRequest,
+)
+
+log = get_logger("swarm.teardown")
+
+router = APIRouter()
+
+
+@router.post("/teardown", response_model=DeployResponse, tags=["Swarm Deployments"])
+async def api_teardown_swarm(
+    req: TeardownRequest,
+    repo: BaseRepository = Depends(get_repo),
+) -> DeployResponse:
+    if req.host_uuid is not None:
+        row = await repo.get_swarm_host_by_uuid(req.host_uuid)
+        if row is None:
+            raise HTTPException(status_code=404, detail="host not found")
+        targets = [row]
+    else:
+        targets = await repo.list_swarm_hosts()
+
+    async def _call(host: dict[str, Any]) -> HostResult:
+        try:
+            async with AgentClient(host=host) as agent:
+                body = await agent.teardown(req.decky_id)
+            if req.decky_id is None:
+                await repo.delete_decky_shards_for_host(host["uuid"])
+            return HostResult(host_uuid=host["uuid"], host_name=host["name"], ok=True, detail=body)
+        except Exception as exc:
+            log.exception("swarm.teardown failed host=%s", host["name"])
+            return HostResult(
+                host_uuid=host["uuid"], host_name=host["name"], ok=False, detail=str(exc)
+            )
+
+    results = await asyncio.gather(*(_call(h) for h in targets))
+    return DeployResponse(results=list(results))