(feature) queue manual backups from the Django host page

Add a staff-only manual backup form to host detail pages with safe
dry-run defaults and optional retention settings.

Queue manual BackupRun records through the existing worker-backed runner
path instead of executing backups inside the web request.

Validate disabled hosts, missing global config, and invalid methods with
view tests covering the new UI flow.

src/pobsync_backend/views.py

@@ -10,7 +10,8 @@ from django.views.decorators.http import require_POST
 
 from pobsync.errors import ConfigError
 
-from .forms import CreateHostConfigForm, GlobalConfigForm, HostConfigForm, ScheduleConfigForm
+from .backup_runner import queue_backup_run
+from .forms import CreateHostConfigForm, GlobalConfigForm, HostConfigForm, ManualBackupForm, ScheduleConfigForm
 from .models import BackupRun, GlobalConfig, HostConfig, ScheduleConfig, SnapshotRecord
 from .retention import run_sql_retention_plan
 from .snapshot_discovery import discover_snapshots
@@ -90,6 +91,7 @@ def host_detail(request, host: str):
     context = {
         "host": host_config,
         "schedule": _schedule_for_host(host_config),
+        "manual_backup_form": ManualBackupForm(initial=_default_manual_backup_initial(host_config)),
         "latest_runs": host_config.runs.select_related("snapshot").order_by("-created_at")[:10],
         "snapshots": host_config.snapshots.select_related("base").order_by("-started_at", "dirname")[:20],
         "counts": {
@@ -102,6 +104,33 @@ def host_detail(request, host: str):
     return render(request, "pobsync_backend/host_detail.html", context)
 
 
+@staff_member_required
+@require_POST
+def queue_manual_backup(request, host: str):
+    host_config = get_object_or_404(HostConfig, host=host)
+    if not host_config.enabled:
+        messages.error(request, f"Cannot queue backup for disabled host {host_config.host}.")
+        return redirect("host_detail", host=host_config.host)
+    if not GlobalConfig.objects.filter(name="default").exists():
+        messages.error(request, "Create the default global config before queueing backups.")
+        return redirect("host_detail", host=host_config.host)
+
+    form = ManualBackupForm(request.POST)
+    if not form.is_valid():
+        messages.error(request, "Manual backup options are invalid.")
+        return redirect("host_detail", host=host_config.host)
+
+    run = queue_backup_run(
+        host=host_config,
+        dry_run=form.cleaned_data["dry_run"],
+        prune=form.cleaned_data["prune"],
+        prune_max_delete=form.cleaned_data["prune_max_delete"],
+        prune_protect_bases=form.cleaned_data["prune_protect_bases"],
+    )
+    messages.success(request, f"Queued manual backup run {run.id} for {host_config.host}.")
+    return redirect("run_detail", run_id=run.id)
+
+
 @staff_member_required
 def run_detail(request, run_id: int):
     run = get_object_or_404(BackupRun.objects.select_related("host", "snapshot"), id=run_id)
@@ -257,5 +286,15 @@ def _default_host_initial() -> dict[str, object]:
     }
 
 
+def _default_manual_backup_initial(host_config: HostConfig) -> dict[str, object]:
+    schedule = _schedule_for_host(host_config)
+    return {
+        "dry_run": True,
+        "prune": bool(schedule.prune) if schedule else False,
+        "prune_max_delete": schedule.prune_max_delete if schedule else 10,
+        "prune_protect_bases": bool(schedule.prune_protect_bases) if schedule else False,
+    }
+
+
 def _pretty_json(value: object) -> str:
     return json.dumps(value or {}, indent=2, sort_keys=True)