feat(android-terminal): Phase F — kiosk, immersive, queued-action toast

Closes out the Android terminal plan (Phases A → F).

- MainActivity:
  * Immersive mode via WindowInsetsControllerCompat — hides status +
    navigation bars, swipe-to-reveal with auto-hide
    (BEHAVIOR_SHOW_TRANSIENT_BARS_BY_SWIPE). Re-applied in onResume so
    a transient overlay can't leave the bars visible.
  * Lock Task Mode — startLockTask() in onResume. The manifest already
    declares lockTaskMode="if_whitelisted", so this enters kiosk on a
    properly MDM-provisioned tablet and is a silent no-op (caught
    SecurityException) on dev / unprovisioned devices.

- TerminalScreen:
  * SnackbarHost pinned at the bottom; LaunchedEffect(actionResult)
    shows "Queued — will sync when back online" whenever an offline
    action gets queued, so the cashier has explicit feedback beyond the
    top-bar pending pill.
  * 4 new locale strings (en/fr/de/lb) for the snackbar copy.

- Manifest cleanup: dropped redundant tools:replace from the debug
  AndroidManifest overlay (networkSecurityConfig isn't set in the main
  manifest, so the replace directive was a no-op + emitted a warning).

Skipped from the plan: a custom splash screen (the existing theme
background renders for the cold-start frame; adding the splashscreen
library is polish for a follow-up) and per-action success toasts
(the action sheet closing + balance refresh + recent-feed update are
adequate confirmation).

Verified by ./gradlew assembleDebug — clean build.

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

clients/terminal-android/app/src/debug/AndroidManifest.xml

@@ -1,10 +1,8 @@
 <?xml version="1.0" encoding="utf-8"?>
-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:tools="http://schemas.android.com/tools">
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <!-- Debug-only manifest overlay. Merged onto the main manifest by AGP for
          debug builds; release builds skip this and keep the platform default
          (no cleartext HTTP). -->
     <application
-        android:networkSecurityConfig="@xml/network_security_config"
-        tools:replace="android:networkSecurityConfig" />
+        android:networkSecurityConfig="@xml/network_security_config" />
 </manifest>