kiosk: integrate BLE scale gateway + fix logo/branding

- Kiosk v1.6.0 (versionCode 10)
  - Integrate BLE scale gateway directly into kiosk app (no external app needed)
    - New scale/ package: BleScaleManager, GatewayWebSocketServer, ScaleProtocol, GatewayService
    - GatewayService: foreground service, runs BLE scan + WebSocket :8765 server
    - Auto-reconnect on BLE disconnect; protocol compatible with old gateway app
  - Setup step 4: replace gateway install flow with BLE device scan + selection (mandatory)
  - Permissions: added BLUETOOTH_SCAN, BLUETOOTH_CONNECT, ACCESS_FINE_LOCATION (pre-S),
    FOREGROUND_SERVICE, FOREGROUND_SERVICE_CONNECTED_DEVICE
  - KioskActivity: replace launchGatewayInBackground() with startGatewayService()
  - checkForUpdates: remove gateway APK check (gateway is now internal)
  - Remove GATEWAY_PACKAGE / GATEWAY_DOWNLOAD_URL constants

- Logo / branding
  - logo.png + logo_icon.png: transparent background (no more black)
  - ic_logo.png regenerated in all densities
  - Removed house emoji (🏠) from web UI: favicon, bottom nav, setup wizard header
  - Removed 🏠 prefix from all translations (it/en/de) and manifest
  - Setup wizard: logo shown in language + welcome steps
  - Setup wizard: footer with credits ('Creato da Stimpfl Daniel • Open Source')
  - CSS: .nav-logo-icon for bottom nav logo sizing

- Scale Gateway v2.1.1 (versionCode 8)
  - Fix false update notification: replace == comparison with proper semverNewer()
    (was reporting 'update available' whenever tag != current, e.g. v2.1.0 != 2.1.0)

assets/css/style.css

@@ -2575,6 +2575,16 @@ body {
 
 .nav-icon {
     font-size: 1.4rem;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+}
+
+.nav-logo-icon {
+    height: 24px;
+    width: auto;
+    object-fit: contain;
+    display: block;
 }
 
 .nav-label {