Scalar Presence: brand-panel login (light/dark), Poppins, splash and launcher icons, fixed API base via dart-define, keep-signed-in, Android project

- Login reworked to the Brand panel layout with a dark-theme switch; 'Scalar Presence' two-line wordmark
- Android project now tracked (was gitignored); pins shared_preferences_android 2.4.27 (2.5.0 crashed with a black screen)
- API base URL fixed per build (--dart-define=API_BASE_URL), no in-app server setting

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pubspec.yaml

@@ -10,14 +10,49 @@ dependencies:
   flutter:
     sdk: flutter
   http: ^1.2.0
+  url_launcher: ^6.3.0
   shared_preferences: ^2.2.0
+  # 2.5.x crashes at start on release builds with Flutter 3.44 (NoSuchMethodError via JNI); POS uses 2.4.27 fine
+  shared_preferences_android: 2.4.27
   intl: ^0.19.0
   geolocator: ^13.0.1
   image_picker: ^1.1.2
   cupertino_icons: ^1.0.6
 
 dev_dependencies:
+  flutter_launcher_icons: ^0.14.0
+  flutter_native_splash: ^2.4.0
   flutter_lints: ^4.0.0
 
+flutter_launcher_icons:
+  android: true
+  ios: false
+  image_path: "assets/brand/scalar-mark.png"
+  adaptive_icon_background: "#FFFFFF"
+  adaptive_icon_foreground: "assets/brand/scalar-mark-maskable.png"
+  min_sdk_android: 21
+
+flutter_native_splash:
+  color: "#FFFFFF"
+  image: assets/brand/scalar-mark.png
+  android_12:
+    color: "#FFFFFF"
+    image: assets/brand/scalar-mark-android12.png
+    icon_background_color: "#FFFFFF"
+  ios: false
+  web: false
+
 flutter:
   uses-material-design: true
+  assets:
+    - assets/brand/
+  fonts:
+    - family: Poppins
+      fonts:
+        - asset: assets/fonts/poppins/Poppins-Regular.ttf
+        - asset: assets/fonts/poppins/Poppins-Medium.ttf
+          weight: 500
+        - asset: assets/fonts/poppins/Poppins-SemiBold.ttf
+          weight: 600
+        - asset: assets/fonts/poppins/Poppins-Bold.ttf
+          weight: 700