fix(rotate): record PPSK rotation password + sync banded-SSID siblings

Three bugs reported from prod after a PPSK rotation:

1. unifi.password_rotation.last_password was only saved after a
   whole-SSID rotation. PPSK-only setups (the typical guest-WiFi case)
   ran a successful rotation but the setting stayed empty, so the
   Settings → Tasks UI never showed the current password and the
   /api/unifi/wifi/current-password endpoint returned 404
   "no rotated password recorded yet". The PPSK loop now writes
   last_password on every successful PPSK rotation.

2. When an SSID is "banded" (band-steering disabled), UniFi splits it
   into one wlanconf per band — 2.4GHz and 5GHz each get their own _id
   and their own embedded PPSK array. Rotating the PPSK on one band
   left the other band with the old password. New
   UnifiApiClient::getWlanSiblings($wlanId) finds all wlanconfs that
   share an SSID name; both rotation and the manual modal edit now
   call updateEmbeddedPpsk on each sibling and update the matching
   UnifiPpsk DB rows.

3. The manual WiFi modal edit had the same band-blindness as #2 —
   editing the GUEST PPSK on the 2.4GHz half left the 5GHz half stale.
   WifiController::ppskUpdate now walks siblings the same way.

v1.8.1.

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": "1.8.0",
+    "version": "1.8.1",
     "type": "library",
     "license": "MIT",
     "autoload": {