Show live progress while pruning networks, and ask first (0.63.0)

The network prune joins the image and volume prunes on the shared
PruneJob: it runs in the background, the Networks page shows a progress
bar and a toast with the outcome, and the button now asks before deleting
instead of pruning on click. Docker has no -a for networks and they hold
no data, so there is no option and no space figure.

Candidates are stricter than docker network prune, which goes by active
endpoints and so removes a stopped container's network, after which that
container fails to start ("network not found"). A network any container,
running or stopped, is attached to (by name or id) is kept, as are
bridge/host/none, ingress/docker_gwbridge and swarm-scoped networks.
Removal is per network, so one the daemon refuses does not stop the rest.

- POST /api/networks/prune takes background=; without it it still waits
  and returns {NetworksDeleted}. GET /api/networks/prune-status is
  admin-only and registered before /{network_id}, which would otherwise
  take "prune-status" for an id.
- The long-timeout test for network prune in test_docker_timeouts.py is
  superseded by test_network_prune.py.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/services/network_service.py

@@ -1,15 +1,18 @@
 """Docker network management."""
 from __future__ import annotations
 
-from typing import Optional
+from typing import Callable, Optional
 
 from docker.errors import APIError
 from docker.types import IPAMConfig, IPAMPool
 
 from docker_client import DockerError, get_client, get_long_client, safe_call
+from services.prune_job import PruneJob, PrunePlan
 
 COMPOSE_PROJECT_LABEL = "com.docker.compose.project"
 DEFAULT_NETWORKS = {"bridge", "host", "none"}
+#: Networks the daemon manages for swarm; never a prune's to remove.
+_SWARM_NETWORKS = {"ingress", "docker_gwbridge"}
 
 
 def _summary(net) -> dict:
@@ -132,6 +135,65 @@ def delete_network(network_id: str) -> None:
     safe_call(net.remove)
 
 
-def prune_networks() -> dict:
+_prune = PruneJob("network")
+
+
+def prune_status() -> dict:
+    return _prune.status()
+
+
+def _candidates(client) -> list[dict]:
+    """The networks no container, running or stopped, is attached to.
+
+    Stricter than ``docker network prune``, which goes by active endpoints and
+    so removes a stopped container's network, after which that container no
+    longer starts ("network not found").
+    """
+    in_use: set[str] = set()
+    for c in safe_call(client.api.containers, all=True):
+        networks = (c.get("NetworkSettings") or {}).get("Networks") or {}
+        for name, settings in networks.items():
+            in_use.add(name)
+            if (settings or {}).get("NetworkID"):
+                in_use.add(settings["NetworkID"])
+    return [
+        n
+        for n in safe_call(client.api.networks)
+        if n["Name"] not in DEFAULT_NETWORKS | _SWARM_NETWORKS
+        and n.get("Scope", "local") == "local"
+        and n["Name"] not in in_use
+        and n["Id"] not in in_use
+    ]
+
+
+def _plan() -> PrunePlan:
     client = get_long_client()
-    return safe_call(client.networks.prune)
+
+    def remove(network: dict) -> tuple[list, bool]:
+        # The daemon refuses if a container was attached since the listing.
+        safe_call(client.api.remove_network, network["Id"])
+        return [network["Name"]], True
+
+    def finish(names: list) -> tuple[dict, Optional[int]]:
+        # Networks hold no data: nothing to measure.
+        return {"NetworksDeleted": names}, None
+
+    return PrunePlan(
+        all=False,
+        items=_candidates(client),
+        label=lambda network: network["Name"],
+        remove=remove,
+        finish=finish,
+    )
+
+
+def prune_networks() -> dict:
+    """Remove unused networks and wait for the result. Progress is visible
+    through prune_status() while it runs."""
+    return _prune.run(_plan)
+
+
+def start_prune(on_done: Optional[Callable[[dict], None]] = None) -> dict:
+    """Start a prune in the background and return its initial status; the UI
+    polls prune_status(). ``on_done`` gets what prune_networks() would return."""
+    return _prune.start(_plan, on_done)