fix: Android app startup — INTERNET permission, MobSF scan, E2E robustness

- Add INTERNET permission to main AndroidManifest.xml (was missing from
  release builds, causing all network calls to fail on device)
- Add scripts/mobsf_scan.sh: uploads release APK to MobSF after each
  build and asserts required permissions are declared; docker pull -q
  suppresses progress-bar noise
- Wire MobSF scan into build-android task; add mobsf-stop convenience task
- Fix _AccountTile subtitle overflow on Android: replace Column([Text,Text])
  with single Text('email\ntype') so ListTile can measure height correctly
- E2E test robustness on Android: use pumpUntil(find.text('Alice')) instead
  of pumpUntil(FAB)+expect to handle Drift background-isolate stream delay;
  add skipOffstage:false to tap; remove stale email-address assertion
- Uninstall app before each Android integration test run to clear leftover
  DB state and prevent "Unable to start the app" on repeated runs
- Update widget tests to use find.textContaining for merged subtitle text

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

android/app/src/main/AndroidManifest.xml

@@ -1,4 +1,5 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+    <uses-permission android:name="android.permission.INTERNET"/>
     <application
         android:label="sharedinbox"
         android:name="${applicationName}"