feat: per-stack storage inventory and portability guardrails (#1399)

* feat: per-stack storage inventory and portability guardrails

Add a Storage tab to the stack Anatomy panel that derives a per-stack mount
inventory (bind mounts, named/anonymous volumes, tmpfs, docker socket;
read-only vs read-write; host-path existence, type, and owner) from the
effective Compose model, and classifies the stack as Portable, Partially
portable, Node-bound, or Unknown with the reasons behind it.

- New GET /api/stacks/:stackName/storage route (stack:read, Community), served
  by an on-demand, non-persisted service that renders the effective model,
  probes within-stack bind sources (symlink-escape aware), and runs the
  deterministic portability classifier.
- Extend the effective-model parser additively with a full per-mount inventory
  and service-level tmpfs, leaving the rule-facing binds/namedVolumes
  byte-identical for the existing preflight rules.
- New anonymous-volume preflight finding.
- Admin-visible "no recent snapshot" warning that reuses the existing hub-local
  snapshot-coverage endpoint, plus a static note distinguishing config
  snapshots from application-data backups.
- Surface storage assumptions in the Stack Dossier markdown export.
- Gate the tab behind a new compose-storage capability on both sides.

* docs: phrase the Storage tab availability as current behavior

Replace the "older Sencho version / until it is updated" wording in the
Storage feature page with present-tense, capability-based phrasing.

backend/src/__tests__/compose-network-inspector.test.ts

@@ -15,7 +15,7 @@ import { assembleStackNetworkFacts } from '../services/network/composeNetworkIns
 
 function effSvc(over: Partial<EffService> = {}): EffService {
   return {
-    name: 'web', image: 'nginx:1.27', ports: [], binds: [], namedVolumes: [],
+    name: 'web', image: 'nginx:1.27', ports: [], binds: [], namedVolumes: [], storageMounts: [],
     privileged: false, hasHealthcheck: true, restart: 'unless-stopped', envKeys: [],
     networks: [], extraHosts: [], labelKeys: [], ...over,
   };