refactor: replace legacy CLI with Django command surface

Retire the old YAML and cron oriented pobsync CLI commands and expose a
SQL-first Django-backed command surface instead. Add schedule and
retention management commands, move shared defaults/parsing out of legacy
commands, remove obsolete command modules, and update documentation and
tests for the new workflow.

src/pobsync_backend/management/commands/configure_pobsync_global.py

@@ -6,8 +6,8 @@ from typing import Any
 from django.conf import settings
 from django.core.management.base import BaseCommand, CommandError
 
-from pobsync.cli import parse_retention
-from pobsync.commands.install import DEFAULT_EXCLUDES, DEFAULT_RSYNC_ARGS
+from pobsync.config.retention import parse_retention
+from pobsync.config.defaults import DEFAULT_EXCLUDES, DEFAULT_RSYNC_ARGS
 from pobsync.util import is_absolute_non_root
 from pobsync_backend.models import GlobalConfig
 

src/pobsync_backend/management/commands/configure_pobsync_host.py

@@ -4,7 +4,7 @@ from typing import Any
 
 from django.core.management.base import BaseCommand, CommandError
 
-from pobsync.cli import parse_retention
+from pobsync.config.retention import parse_retention
 from pobsync.util import sanitize_host
 from pobsync_backend.models import GlobalConfig, HostConfig
 

src/pobsync_backend/management/commands/configure_pobsync_schedule.py

@@ -0,0 +1,55 @@
+from __future__ import annotations
+
+from typing import Any
+
+from django.core.management.base import BaseCommand, CommandError
+
+from pobsync_backend.models import HostConfig, ScheduleConfig
+from pobsync_backend.scheduler import parse_cron_expr
+
+
+class Command(BaseCommand):
+    help = "Create, update, disable, or remove a SQL-backed pobsync schedule."
+
+    def add_arguments(self, parser) -> None:
+        parser.add_argument("host")
+        parser.add_argument("--cron", help='Cron expression, e.g. "15 2 * * *"')
+        parser.add_argument("--user", default="root")
+        parser.add_argument("--prune", action="store_true")
+        parser.add_argument("--prune-max-delete", type=int, default=10)
+        parser.add_argument("--prune-protect-bases", action="store_true")
+        parser.add_argument("--disabled", action="store_true")
+        parser.add_argument("--delete", action="store_true")
+
+    def handle(self, *args: Any, **options: Any) -> None:
+        try:
+            host = HostConfig.objects.get(host=options["host"])
+        except HostConfig.DoesNotExist as exc:
+            raise CommandError(f"Missing HostConfig {options['host']!r}") from exc
+
+        if options["delete"]:
+            deleted, _details = ScheduleConfig.objects.filter(host=host).delete()
+            self.stdout.write(self.style.SUCCESS(f"Deleted {deleted} schedule row(s) for {host.host!r}."))
+            return
+
+        if not options["cron"]:
+            raise CommandError("--cron is required unless --delete is used")
+        try:
+            parse_cron_expr(options["cron"])
+        except ValueError as exc:
+            raise CommandError(str(exc)) from exc
+
+        schedule, created = ScheduleConfig.objects.update_or_create(
+            host=host,
+            defaults={
+                "cron_expr": options["cron"],
+                "user": options["user"],
+                "enabled": not options["disabled"],
+                "prune": bool(options["prune"]),
+                "prune_max_delete": int(options["prune_max_delete"]),
+                "prune_protect_bases": bool(options["prune_protect_bases"]),
+            },
+        )
+        action = "Created" if created else "Updated"
+        state = "enabled" if schedule.enabled else "disabled"
+        self.stdout.write(self.style.SUCCESS(f"{action} {state} schedule for {host.host!r}."))

src/pobsync_backend/management/commands/run_pobsync_retention.py

@@ -0,0 +1,55 @@
+from __future__ import annotations
+
+import json
+from pathlib import Path
+from typing import Any
+
+from django.conf import settings
+from django.core.management.base import BaseCommand, CommandError
+
+from pobsync.commands.retention_apply import run_retention_apply
+from pobsync.commands.retention_plan import run_retention_plan
+from pobsync_backend.config_source import DjangoConfigSource
+from pobsync_backend.models import HostConfig
+
+
+class Command(BaseCommand):
+    help = "Plan or apply retention using SQL-backed pobsync configuration."
+
+    def add_arguments(self, parser) -> None:
+        parser.add_argument("host")
+        parser.add_argument("--prefix", default=settings.POBSYNC_HOME)
+        parser.add_argument("--kind", default="scheduled", choices=["scheduled", "manual", "all"])
+        parser.add_argument("--protect-bases", action="store_true")
+        parser.add_argument("--apply", action="store_true")
+        parser.add_argument("--yes", action="store_true")
+        parser.add_argument("--max-delete", type=int, default=10)
+
+    def handle(self, *args: Any, **options: Any) -> None:
+        host = options["host"]
+        if not HostConfig.objects.filter(host=host, enabled=True).exists():
+            raise CommandError(f"Missing enabled HostConfig {host!r}")
+
+        config_source = DjangoConfigSource()
+        if options["apply"]:
+            if not options["yes"]:
+                raise CommandError("--yes is required with --apply")
+            result = run_retention_apply(
+                prefix=Path(options["prefix"]),
+                host=host,
+                kind=options["kind"],
+                protect_bases=bool(options["protect_bases"]),
+                yes=True,
+                max_delete=int(options["max_delete"]),
+                config_source=config_source,
+            )
+        else:
+            result = run_retention_plan(
+                prefix=Path(options["prefix"]),
+                host=host,
+                kind=options["kind"],
+                protect_bases=bool(options["protect_bases"]),
+                config_source=config_source,
+            )
+
+        self.stdout.write(json.dumps(result, indent=2, sort_keys=False))