refactor: use injected config sources for retention

Allow retention planning and pruning to use the same ConfigSource
abstraction as scheduled backups. This removes the remaining SQL-to-YAML
export dependency from Django backup runs with pruning, keeping YAML only
as a legacy CLI compatibility path.

src/pobsync/commands/retention_apply.py

@@ -4,6 +4,7 @@ import shutil
 from pathlib import Path
 from typing import Any, Dict, List
 
+from ..config.source import ConfigSource
 from ..errors import ConfigError
 from ..lock import acquire_host_lock
 from ..paths import PobsyncPaths
@@ -19,6 +20,7 @@ def run_retention_apply(
     yes: bool,
     max_delete: int,
     acquire_lock: bool = True,
+    config_source: ConfigSource | None = None,
 ) -> dict[str, Any]:
     host = sanitize_host(host)
 
@@ -34,7 +36,13 @@ def run_retention_apply(
     paths = PobsyncPaths(home=prefix)
 
     def _do_apply() -> dict[str, Any]:
-        plan = run_retention_plan(prefix=prefix, host=host, kind=kind, protect_bases=bool(protect_bases))
+        plan = run_retention_plan(
+            prefix=prefix,
+            host=host,
+            kind=kind,
+            protect_bases=bool(protect_bases),
+            config_source=config_source,
+        )
 
         delete_list = plan.get("delete") or []
         if not isinstance(delete_list, list):
@@ -100,4 +108,3 @@ def run_retention_apply(
 
     # Caller guarantees locking (used by run-scheduled)
     return _do_apply()
-

src/pobsync/commands/retention_plan.py

@@ -4,8 +4,7 @@ from datetime import datetime, timezone
 from pathlib import Path
 from typing import Any, Dict, List, Optional, Tuple
 
-from ..config.load import load_global_config, load_host_config
-from ..config.merge import build_effective_config
+from ..config.source import ConfigSource, FileConfigSource
 from ..errors import ConfigError
 from ..paths import PobsyncPaths
 from ..retention import Snapshot, build_retention_plan
@@ -82,7 +81,13 @@ def _apply_base_protection(
     return keep, reasons
 
 
-def run_retention_plan(prefix: Path, host: str, kind: str, protect_bases: bool) -> dict[str, Any]:
+def run_retention_plan(
+    prefix: Path,
+    host: str,
+    kind: str,
+    protect_bases: bool,
+    config_source: ConfigSource | None = None,
+) -> dict[str, Any]:
     host = sanitize_host(host)
 
     if kind not in {"scheduled", "manual", "all"}:
@@ -90,9 +95,8 @@ def run_retention_plan(prefix: Path, host: str, kind: str, protect_bases: bool)
 
     paths = PobsyncPaths(home=prefix)
 
-    global_cfg = load_global_config(paths.global_config_path)
-    host_cfg = load_host_config(paths.hosts_dir / f"{host}.yaml")
-    cfg = build_effective_config(global_cfg, host_cfg)
+    source = config_source or FileConfigSource(prefix=paths.home)
+    cfg = source.effective_config_for_host(host)
 
     retention = cfg.get("retention")
     if not isinstance(retention, dict):
@@ -161,4 +165,3 @@ def run_retention_plan(prefix: Path, host: str, kind: str, protect_bases: bool)
         ],
         "reasons": reasons,
     }
-

src/pobsync/commands/run_scheduled.py

@@ -276,6 +276,7 @@ def run_scheduled(
                 yes=True,
                 max_delete=10 if prune_max_delete is None else int(prune_max_delete),
                 acquire_lock=False,
+                config_source=source,
             )
 
         return {

src/pobsync_backend/management/commands/run_pobsync_backup.py

@@ -9,7 +9,6 @@ from django.utils import timezone
 
 from pobsync.commands.run_scheduled import run_scheduled
 from pobsync.paths import PobsyncPaths
-from pobsync_backend.config_repository import export_runtime_configs
 from pobsync_backend.config_source import DjangoConfigSource
 from pobsync_backend.models import BackupRun, HostConfig
 
@@ -33,11 +32,6 @@ class Command(BaseCommand):
         except HostConfig.DoesNotExist as exc:
             raise CommandError(f"Missing enabled HostConfig {host_name!r}") from exc
 
-        # Compatibility bridge: retention planning still reads runtime YAML.
-        # The backup run itself receives config directly from Django.
-        if options["prune"]:
-            export_runtime_configs(prefix=paths.home, host=host.host)
-
         run = BackupRun.objects.create(
             host=host,
             run_type=BackupRun.RunType.SCHEDULED,

src/pobsync_backend/tests/test_retention_config_source.py

@@ -0,0 +1,53 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from pathlib import Path
+from tempfile import TemporaryDirectory
+
+from django.test import SimpleTestCase
+
+from pobsync.commands.retention_plan import run_retention_plan
+from pobsync.util import write_yaml_atomic
+
+
+class FakeConfigSource:
+    def __init__(self, backup_root: str) -> None:
+        self.backup_root = backup_root
+
+    def effective_config_for_host(self, host: str) -> dict:
+        return {
+            "backup_root": self.backup_root,
+            "host": host,
+            "address": "example.test",
+            "retention": {"daily": 1, "weekly": 0, "monthly": 0, "yearly": 0},
+        }
+
+
+class RetentionConfigSourceTests(SimpleTestCase):
+    def test_retention_plan_uses_injected_config_source(self) -> None:
+        with TemporaryDirectory() as tmp:
+            root = Path(tmp) / "backups"
+            snap_dir = root / "web-01" / "scheduled" / "20260519-021500Z__ABCDEFGH"
+            meta_dir = snap_dir / "meta"
+            meta_dir.mkdir(parents=True)
+            write_yaml_atomic(
+                meta_dir / "meta.yaml",
+                {
+                    "status": "success",
+                    "started_at": datetime(2026, 5, 19, 2, 15, tzinfo=timezone.utc)
+                    .isoformat()
+                    .replace("+00:00", "Z"),
+                },
+            )
+
+            plan = run_retention_plan(
+                prefix=Path("/missing-prefix"),
+                host="web-01",
+                kind="scheduled",
+                protect_bases=False,
+                config_source=FakeConfigSource(str(root)),
+            )
+
+        self.assertTrue(plan["ok"])
+        self.assertEqual(plan["keep"], ["20260519-021500Z__ABCDEFGH"])
+        self.assertEqual(plan["delete"], [])