fix(proxy): forward scoped stack evidence for alerts, auto-heal, and node-wide image refresh (#1749)

* fix(proxy): forward scoped stack evidence for alerts, auto-heal, and node-wide image refresh

Extend the remote proxy scoped-evidence mechanism beyond /stacks/*
routes. Three new gates in runGatedProxy:

- Alerts POST: reuse the already-buffered body from the existing
  isAlertCreateRoute block, extract stack_name, check hub-side
  scoped permission, and forward SCOPED_STACK_AUTH_EVIDENCE headers.
- Auto-heal POST: same pattern with new body buffering and encoding
  rejection (no pre-existing buffering exists for this route).
- Node-wide image refresh: elevate PROXY_ROLE_HEADER to node-admin
  when the user has a scoped node:manage grant on the target node,
  matching the Settings pre-auth gate pattern.

Also extend classifyStackApiPath to recognize
/image-updates/refresh/:stackName as a named-stack route (stack:deploy),
ready for when PR #1743 adds the per-stack refresh endpoint.

Explicitly excluded: ID-based routes (DELETE /alerts/:id,
PATCH/DELETE /auto-heal/policies/:id) where the hub cannot resolve
remote-owned IDs to stack names; GET routes where stack:read is
globally granted to every role; and POST /auto-update/execute where
multi-stack/wildcard targets need a different evidence format.

* chore(proxy): add RBAC diagnostic logging to scoped permission path

Add developer_mode-gated diagnostic logs to checkPermission to expose
which check is failing when a scoped user is denied: effective tier,
DB query parameters, and node-scoped assignment lookups.

* chore(rbac): log effective tier and license status when scoped checks are blocked

Add an always-visible console.warn in checkPermission when the
effective tier prevents scoped role-assignment lookups, logging
both the resolved tier and the raw license_status DB value. This
surfaces the failure reason in container logs without requiring
developer_mode, so QA can diagnose why scoped users are denied.

* chore(rbac): sanitize scoped-tier log values to satisfy CodeQL log-injection check

backend/package-lock.json

@@ -10,7 +10,6 @@
       "hasInstallScript": true,
       "license": "AGPL-3.0-only",
       "dependencies": {
-        "@aws-sdk/client-s3": "3.1097.0",
         "axios": "^1.15.0",
         "bcrypt": "^6.0.0",
         "better-sqlite3": "^13.0.1",