fix: add missing native permissions for biometric auth

iOS was missing NSFaceIDUsageDescription — Face ID prompts will
crash without it (required by Apple since iOS 11). Added with
user-facing reason string scoped to health data privacy.

Android was missing USE_BIOMETRIC and USE_FINGERPRINT permissions —
biometric_local_auth plugin requires both for API 28+/legacy compat.

The Flutter implementation was already complete:
- BiometricService (services/biometric_service.dart)
- AuthGate lock screen (core/auth_gate.dart)
- Settings toggle with policy control (features/settings/)
- Wired into main.dart

These permission declarations were the only missing pieces
blocking Face ID / fingerprint from working on device.

android/app/src/main/AndroidManifest.xml

@@ -2,6 +2,9 @@
     <!-- Permissions for voice input -->
     <uses-permission android:name="android.permission.RECORD_AUDIO"/>
     <uses-permission android:name="android.permission.INTERNET"/>
+    <!-- Biometric authentication -->
+    <uses-permission android:name="android.permission.USE_BIOMETRIC"/>
+    <uses-permission android:name="android.permission.USE_FINGERPRINT"/>
     
     <application
         android:label="inou_mobile"

ios/Runner/Info.plist

@@ -2,6 +2,8 @@
 <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
 <plist version="1.0">
 <dict>
+	<key>NSFaceIDUsageDescription</key>
+	<string>inou uses Face ID to keep your medical data private and secure.</string>
 	<key>CFBundleDevelopmentRegion</key>
 	<string>$(DEVELOPMENT_LANGUAGE)</string>
 	<key>CFBundleDisplayName</key>