feat(sv): Storage · capacity card — ZFS pools, dropped pools, per-CT disk

Read-only Proxmox storage health (same PROXMOX_RO_TOKEN as the cluster card):
ZFS pool health+usage, dropped zfspool storages (the donatello/leonardo SATA
signal), and per-LXC rootfs fill, with a HEALTHY/WATCH/ATTENTION roll-up.
Closes the monitoring gap from the 2026-06-09 audit (C1 + H2 were invisible).
Pure normalizeStorage() unit-tested (4 tests).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/api/routes/storage.js

@@ -0,0 +1,17 @@
+import { Router } from 'express';
+import { asyncWrap } from '../errors.js';
+import { storageHealth } from '../../proxmox/storage.js';
+
+// Read-only storage/capacity health for the Sacred Valley card. Cached briefly so
+// multiple polling clients coalesce into one set of PVE calls. Owner or any authed agent.
+export const router = Router();
+
+let cache = { at: 0, data: null };
+const TTL = 15_000;
+
+router.get('/', asyncWrap(async (_req, res) => {
+  if (cache.data && Date.now() - cache.at < TTL) return res.json(cache.data);
+  const data = await storageHealth();
+  cache = { at: Date.now(), data };
+  res.json(data);
+}));