feat(db): 待处理新增「下载器连不上」「下载目录读不到容量」两类（迁移 0073）

decision.kind 增加 downloader_offline / cache_volume_unknown,契约、原因文案与界面标签同步;
volume_state_unknown 的原因文案改为「下载目录读不到容量」并指向路径映射与容器挂载。

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Cxwgnn2pbzQ7rXv3rq7fei

apps/web/app/components/library/labels.ts

@@ -142,6 +142,8 @@ export const DECISION_KIND: Record<DecisionKind, string> = {
   approval_required: "需要审批",
   metadata_conflict: "元数据冲突",
   source_unreachable: "来源不可达",
+  downloader_offline: "下载器连不上",
+  cache_volume_unknown: "下载目录读不到容量",
   other: "其他",
 };