(ui) Show retention apply details on run detail

Record planned delete counts, max-delete settings, base protection, and
ignored incomplete snapshots in retention apply results.

Surface those details on run detail pages so scheduled and manual prune
outcomes are understandable without reading the raw JSON payload.

src/pobsync_backend/retention.py

@@ -78,8 +78,11 @@ def run_sql_retention_apply(
     def _do_apply() -> dict[str, Any]:
         plan = run_sql_retention_plan(host=host, kind=kind, protect_bases=bool(protect_bases))
         delete_list = plan.get("delete") or []
+        incomplete_list = plan.get("incomplete") or []
         if not isinstance(delete_list, list):
             raise ConfigError("Invalid retention plan output: delete is not a list")
+        if not isinstance(incomplete_list, list):
+            raise ConfigError("Invalid retention plan output: incomplete is not a list")
         if max_delete == 0 and len(delete_list) > 0:
             raise ConfigError("Deletion blocked by --max-delete=0")
         if len(delete_list) > max_delete:
@@ -116,6 +119,8 @@ def run_sql_retention_apply(
             "protect_bases": bool(protect_bases),
             "max_delete": max_delete,
             "source": "sql",
+            "planned_delete_count": len(delete_list),
+            "incomplete_ignored_count": len(incomplete_list),
             "deleted": deleted,
             "actions": actions,
         }