Show live progress while pruning volumes, and ask first (0.62.0)

The volume prune gets the same treatment as the image prune in 0.61.0:
the candidates are listed and removed one by one in the background, and
the Volumes page shows a progress bar (x / y, the volume being removed,
failures) followed by a toast with the space freed.

The button also used to delete without asking, and a bare docker volume
prune only removes anonymous volumes on Engine 23+ with no way to include
named ones. It now opens a confirmation dialog with an explicit -a option
that warns it also takes the data of every stack that is down.

- Candidates: volumes no container (running or stopped) mounts, local
  scope only, and anonymous (com.docker.volume.anonymous) unless -a.
  Volumes from pre-23 daemons carry no such label, so they only go with
  -a, which errs on the side of keeping data.
- Removed without force, so a volume mounted since the listing is
  refused; one refusal does not stop the rest.
- No closing daemon prune: nothing is left over, and on a pre-23 daemon an
  unfiltered one would delete named volumes too.
- Freed space is the sum of the deleted volumes' sizes (volumes share no
  data), from the size cache, which is invalidated afterwards.
- POST /api/volumes/prune takes all= and background=; without background
  it still waits and returns {VolumesDeleted, SpaceReclaimed}.
  GET /api/volumes/prune-status is admin-only.
- volume_sizes() ("Compute sizes") now uses the long-timeout client; it
  walks every volume and could hit the same 60s limit.

The progress machinery moved into services/prune_job.py (PruneJob,
PrunePlan) and, on the frontend, the usePruneJob hook and PruneProgress
component, shared by both pages. The status now carries a phase
(preparing / removing / finishing) so the parts without a count say what
they are doing.

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

backend/routers/images.py

@@ -11,6 +11,7 @@ from database import engine, get_session
 from models.image_scan import ImageScan, ScanDetail, ScanRequest, ScanSummary
 from models.user import User
 from services import audit_service, image_service, scan_service, update_service
+from services.prune_job import PruneBusy
 
 router = APIRouter(prefix="/api/images", tags=["images"])
 
@@ -69,7 +70,7 @@ def prune(
             response.status_code = 202
             return image_service.start_prune(all_unused, on_done=audit)
         result = image_service.prune_images(all_unused)
-    except image_service.PruneBusy as exc:
+    except PruneBusy as exc:
         raise HTTPException(status_code=409, detail=str(exc)) from exc
     audit(result)
     return result

backend/routers/volumes.py

@@ -1,13 +1,14 @@
 """Volume management, NFS/SMB YAML generation, and host path browser."""
 from __future__ import annotations
 
-from fastapi import APIRouter, Depends, HTTPException, Query, Request
+from fastapi import APIRouter, Depends, HTTPException, Query, Request, Response
 from sqlmodel import Session
 
 from auth import get_current_user, require_admin
-from database import get_session
+from database import engine, get_session
 from models.user import User
 from services import audit_service, device_service, volume_service
+from services.prune_job import PruneBusy
 
 router = APIRouter(tags=["volumes"])
 
@@ -67,17 +68,45 @@ def delete_volume(
 @router.post("/api/volumes/prune")
 def prune(
     request: Request,
-    session: Session = Depends(get_session),
+    response: Response,
+    all_unused: bool = Query(False, alias="all"),
+    background: bool = Query(False),
     user: User = Depends(require_admin),
 ) -> dict:
-    result = volume_service.prune_volumes()
-    audit_service.record(
-        session, user=user.username, action="volume.prune", target="*",
-        detail=str(result.get("VolumesDeleted")), ip=_ip(request),
-    )
+    """Remove unused volumes: anonymous ones, or with ``all=true`` named ones
+    too (``-a``).
+
+    Waits for the result by default. ``background=true`` returns 202 with the
+    initial status at once and leaves the caller to poll /prune-status, which
+    is what the UI does: a large prune can outlast the proxy's read timeout.
+    """
+    username, ip = user.username, _ip(request)
+
+    def audit(result: dict) -> None:
+        # Its own session: in the background case the request's is long closed.
+        with Session(engine) as own:
+            audit_service.record(
+                own, user=username, action="volume.prune", target="*",
+                detail=f"all={all_unused} deleted={result['VolumesDeleted']}", ip=ip,
+            )
+
+    try:
+        if background:
+            response.status_code = 202
+            return volume_service.start_prune(all_unused, on_done=audit)
+        result = volume_service.prune_volumes(all_unused)
+    except PruneBusy as exc:
+        raise HTTPException(status_code=409, detail=str(exc)) from exc
+    audit(result)
     return result
 
 
+@router.get("/api/volumes/prune-status")
+def prune_status(_admin: User = Depends(require_admin)) -> dict:
+    """Progress of a running (or the last) prune. Admin-only like the prune."""
+    return volume_service.prune_status()
+
+
 @router.post("/api/volumes/generate-yaml")
 def generate_yaml(
     spec: dict,