fix: kiosk title center + location pref 2 uses + update confirm before download

app.js:
- _injectKioskOverlay: move kiosk-mode class assignment BEFORE the
  _kiosk_overlay existence guard — fixes race where Kotlin onPageFinished
  injects buttons during the await api() pause, then JS skips the class
- _PREF_LOC_NEEDED: 3 → 2 (remember use-location after 2 picks, not 3)

KioskActivity.kt:
- showNativeUpdateBanner: remove auto-start of triggerApkDownload;
  banner now shows with 'Scarica' button enabled, download only starts
  when user taps it (confirms before install)

evershelf-kiosk/app/src/main/kotlin/it/dadaloop/evershelf/kiosk/KioskActivity.kt

@@ -538,10 +538,11 @@ class KioskActivity : AppCompatActivity() {
     private fun showNativeUpdateBanner(message: String, apkDownloadUrl: String) {
         pendingApkDownloadUrl = apkDownloadUrl
         tvUpdateMessage.text = "⬆️ Aggiornamento disponibile:  $message"
+        // Reset button to initial state so user can confirm before download starts
+        btnInstallUpdate.isEnabled = true
+        btnInstallUpdate.text = "⬇ Scarica"
         updateBanner.visibility = View.VISIBLE
-        // Auto-start download immediately — no timer hide, stays until done or dismissed
-        activeInstallBtn = btnInstallUpdate
-        triggerApkDownload(apkDownloadUrl)
+        // Download starts only when the user taps btnInstallUpdate
     }
 
     // ── APK Download + Install ─────────────────────────────────────────────