feat(access): strict allowlist + add groups by search

* UnifiPageGrant::userCanAccess no longer falls back to "open" when a
  page has no grants saved. Pages now require an explicit grant for
  every non-super-admin user — either a direct user grant or via a
  group they belong to. Matches the new dashboard-wide access model.
* Route enforcement returns 404 (was 403) so ungranted users can't even
  confirm the page exists.
* New /settings/pages-access/groups/search endpoint mirrors the
  user typeahead. Groups are no longer all listed by default — only
  super-admin groups (locked-on) and groups with at least one existing
  grant show up in the matrix. Operators add more via search.

v1.7.1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

composer.json

@@ -1,7 +1,7 @@
 {
     "name": "dashboard/unifi",
     "description": "UniFi network management, WiFi stats, and captive portal authentication for the Dashboard platform",
-    "version": "1.7.0",
+    "version": "1.7.1",
     "type": "library",
     "license": "MIT",
     "autoload": {