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/tests/test_console_entrypoint.py

@@ -0,0 +1,41 @@
+from __future__ import annotations
+
+from io import StringIO
+from unittest.mock import patch
+
+from django.test import SimpleTestCase
+
+from pobsync.cli import main
+
+
+class ConsoleEntrypointTests(SimpleTestCase):
+    def test_maps_backup_alias_to_django_command(self) -> None:
+        with patch("pobsync.cli.execute_from_command_line") as execute:
+            exit_code = main(["backup", "web-01", "--dry-run"])
+
+        self.assertEqual(exit_code, 0)
+        execute.assert_called_once_with(["pobsync", "run_pobsync_backup", "web-01", "--dry-run"])
+
+    def test_unknown_command_returns_usage_error(self) -> None:
+        stderr = StringIO()
+        with patch("sys.stderr", stderr):
+            exit_code = main(["run-scheduled", "web-01"])
+
+        self.assertEqual(exit_code, 2)
+        self.assertIn("Unknown pobsync command", stderr.getvalue())
+
+    def test_django_passthrough_keeps_management_command_name(self) -> None:
+        with patch("pobsync.cli.execute_from_command_line") as execute:
+            exit_code = main(["django", "check"])
+
+        self.assertEqual(exit_code, 0)
+        execute.assert_called_once_with(["pobsync", "check"])
+
+    def test_maps_schedule_alias_to_django_command(self) -> None:
+        with patch("pobsync.cli.execute_from_command_line") as execute:
+            exit_code = main(["schedule", "web-01", "--cron", "15 2 * * *"])
+
+        self.assertEqual(exit_code, 0)
+        execute.assert_called_once_with(
+            ["pobsync", "configure_pobsync_schedule", "web-01", "--cron", "15 2 * * *"]
+        )