## Summary

- Fall back to filesystem measurement when snapshot storage metadata is missing.
- Prefer `data/` inside snapshot directories so incomplete snapshot metadata/log files are not counted as backup data.
- Add stats and dashboard rendering coverage for incomplete snapshots without recorded storage metadata.

## Tests
- .venv/bin/python manage.py test src.pobsync_backend.tests.test_stats_summary src.pobsync_backend.tests.test_views.ViewTests.test_dashboard_host_cards_measure_incomplete_data_without_snapshot_metadata --verbosity 2
- .venv/bin/python manage.py check
- git diff --check
- .venv/bin/python manage.py test src.pobsync_backend --verbosity 2

Closes #62

src/pobsync_backend/stats_summary.py

@@ -5,7 +5,7 @@ from typing import Any, Iterable
 
 from django.utils import timezone
 
-from pobsync.run_stats import filesystem_capacity
+from pobsync.run_stats import filesystem_capacity, tree_usage
 
 from .models import BackupRun, GlobalConfig, HostConfig, SnapshotRecord
 
@@ -168,6 +168,12 @@ def _snapshot_summary(snapshot: SnapshotRecord | None) -> dict[str, Any]:
     stats = metadata.get("stats") if isinstance(metadata.get("stats"), dict) else {}
     storage = stats.get("storage") if isinstance(stats.get("storage"), dict) else {}
     snapshot_storage = storage.get("snapshot") if isinstance(storage.get("snapshot"), dict) else {}
+    has_recorded_size = (
+        _int_at(snapshot_storage, "allocated_size_bytes") is not None
+        or _int_at(snapshot_storage, "apparent_size_bytes") is not None
+    )
+    if not has_recorded_size:
+        snapshot_storage = _snapshot_storage_from_filesystem(snapshot)
     return {
         "id": snapshot.id,
         "dirname": snapshot.dirname,
@@ -180,6 +186,18 @@ def _snapshot_summary(snapshot: SnapshotRecord | None) -> dict[str, Any]:
     }
 
 
+def _snapshot_storage_from_filesystem(snapshot: SnapshotRecord) -> dict[str, Any]:
+    if not snapshot.path:
+        return {}
+    snapshot_path = Path(snapshot.path)
+    data_path = snapshot_path / "data"
+    if snapshot_path.name == "data":
+        return tree_usage(snapshot_path)
+    if data_path.exists():
+        return tree_usage(data_path)
+    return tree_usage(snapshot_path)
+
+
 def _is_real_run(run: BackupRun) -> bool:
     result = run.result if isinstance(run.result, dict) else {}
     if result.get("dry_run") is True: