feat(mobile): Add biometric lock for app resume (#1474)

* Feature: Biometric lock for app resume

User enables "Biometric Lock" in Settings → prompted to verify fingerprint/face first.
User backgrounds the app → _isLocked = true.
User returns → lock screen appears, auto-triggers biometric prompt.
Success → app unlocks, state preserved underneath.
Can retry or log out as fallback.
Add USE_BIOMETRIC permission to AndroidManifest.

* Fix: Remove duplicate local_auth entry in pubspec.lock and add NSFaceIDUsageDescription to iOS Info.plist

* fix(mobile) : Remove duplicate local auth files first

* fix(mobile): keep MainNavigationScreen in the Stack, let the lock screen float above, no unmounting

* Updtae: Swap out Flutter Activity for FlutterFragmentActivity that extends the lock scan feature

* fix(mobile): address biometric lock PR review feedback

* fix(mobile): only require biometric auth when enabling lock, not disabling

Prevents users from getting locked out if biometrics start failing —
they can now disable the lock without needing to pass biometric auth.

* fix(mobile): add missing closing brace in setBiometricEnabled

---------

Signed-off-by: Tristan Katana <50181095+felixmuinde@users.noreply.github.com>

mobile/android/app/src/main/AndroidManifest.xml

@@ -2,7 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android">
     
     <uses-permission android:name="android.permission.INTERNET"/>
-    
+    <uses-permission android:name="android.permission.USE_BIOMETRIC"/>
+
     <application
         android:label="Sure Finances"
         android:name="${applicationName}"

mobile/android/app/src/main/kotlin/am/sure/mobile/MainActivity.kt

@@ -1,5 +1,5 @@
 package am.sure.mobile
 
-import io.flutter.embedding.android.FlutterActivity
+import io.flutter.embedding.android.FlutterFragmentActivity
 
-class MainActivity: FlutterActivity()
+class MainActivity: FlutterFragmentActivity()