chore: remove AP Groups surfaces (legacy API auth incompatible)

UniFi's /rest/apgroup endpoints (and per-SSID ap_group_ids writes via
/rest/wlanconf) require session-cookie auth — they don't accept the
X-API-Key header. The Integration API doesn't expose AP groups at all.
So with the current deployment running on API-key auth, every AP-group
operation returned 400 api.err.InvalidObject. Removing the dead code
rather than carrying a feature that can't function.

* Deleted ApGroupController, ApGroups.vue, the /ap-groups/* routes,
  and getApGroups/createApGroup/updateApGroup/deleteApGroup from
  UnifiApiClient.
* Removed the per-SSID AP-group assignment from Wifi.vue + the
  updateApGroups action + /wifi/{wlanId}/ap-groups route + the
  ap_group_ids field from the mapWlan output.
* Removed the AP Groups nav entry from composer.json.

If a future deploy adds local-admin username+password auth, AP groups
can be reintroduced — the UnifiApiClient::buildRequest() session-cookie
path is intact.

v1.3.1.

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

src/Services/UnifiApiClient.php

@@ -312,28 +312,6 @@ class UnifiApiClient
         return $this->put("/rest/wlanconf/{$wlanId}", $data);
     }
 
-    // ── AP Groups ─────────────────────────────────────────────────────────────
-
-    public function getApGroups(): array
-    {
-        return $this->get('/rest/apgroups');
-    }
-
-    public function createApGroup(array $data): array
-    {
-        return $this->post('/rest/apgroups', $data);
-    }
-
-    public function updateApGroup(string $groupId, array $data): array
-    {
-        return $this->put("/rest/apgroups/{$groupId}", $data);
-    }
-
-    public function deleteApGroup(string $groupId): void
-    {
-        $this->delete("/rest/apgroups/{$groupId}");
-    }
-
     // ── PPSK ─────────────────────────────────────────────────────────────────
 
     /**