Gate the guest Wi-Fi card on its own key, and gate its poll endpoint properly

The home card used to be grant-gated by the shell's card table, which left the
poll endpoint behind `auth` alone — and that endpoint returns a LIVE CREDENTIAL:
the guest network's current rotating password and its join QR code. "Any logged-in
user" was never an adequate gate for that; the card table was doing the work, and
the card table is gone.

New key rather than reuse: unifi.guest_wifi exists precisely so front-desk staff
can be given the guest password WITHOUT any other network access. Reusing
unifi.settings would have meant handing out controller configuration to get a
Wi-Fi password read.

Authorised inside the controller rather than by route middleware, so the endpoint
stays outside the unifi page-permission groups — it is a home-page widget, not a
unifi page.

Nobody holds the new key until it is granted, so the card is invisible until then.
That is the intended direction: capability is assigned deliberately.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RDA3fQbsa3gaHCFoV1Q8Gg

composer.json

@@ -35,7 +35,8 @@
                 { "key": "unifi.stats",    "label": "View Network Stats",  "description": "View WiFi dashboards, AP stats, and client lists" },
                 { "key": "unifi.manage",   "label": "Manage Network",      "description": "Reboot APs, manage SSIDs, change WiFi passwords" },
                 { "key": "unifi.auth",     "label": "Manage Portal Auth",  "description": "Configure captive portal, VLAN mappings, MAC allowlist" },
-                { "key": "unifi.settings", "label": "Network Settings",    "description": "Configure UniFi controller connection" }
+                { "key": "unifi.settings", "label": "Network Settings",    "description": "Configure UniFi controller connection" },
+                { "key": "unifi.guest_wifi", "label": "View Guest Wi-Fi Password", "description": "See the guest network name, its current rotating password, and the join QR code on the home page. Grants no other network access." }
             ]
         }
     },