feat: add multi-environment support (development, staging, production)

- Replace dotenv with compile-time dart-define-from-file config per flavor
  - Add Android product flavors with applicationIdSuffix and per-flavor AndroidManifest
  - Add iOS build configurations, schemes, per-flavor plists and entitlements
  - Configure ProGuard rules for R8 compatibility with Entrust/Antelop SDK
  - Restructure assets into shared/ and per-flavor directories
  - Generate per-flavor launcher icons for Android and iOS
  - Refactor app initialization into initApp() with per-flavor entry points
  - Update asset paths across auth, home, profile, splash modules and sf_shared

apps/mobile_app/flutter_native_splash.yaml

@@ -0,0 +1,15 @@
+flutter_native_splash:
+  fullscreen: true
+  color: "#F7F7F7"
+  image: assets/shared/images/logo_splash.png
+  android_gravity: center
+  ios_content_mode: scaleAspectFit
+
+  android: true
+  ios: true
+  web: false
+
+  android_12:
+    color: "#F7F7F7"
+    icon_background_color: "#F7F7F7"
+    image: assets/shared/images/logo_splash.png