chore(demo_spm): replace symlinked gitignore and add flutter_dotenv dep

Git doesn't follow symlinked .gitignore files, so replace with a real
copy. Add missing flutter_dotenv dependency and .env asset needed by
the shared main.dart.

Made-with: Cursor

Author: fadi-george

examples/demo_spm/.gitignore

@@ -0,0 +1,48 @@
+# Miscellaneous
+*.class
+*.log
+*.pyc
+*.swp
+.DS_Store
+.atom/
+.build/
+.buildlog/
+.history
+.svn/
+.swiftpm/
+migrate_working_dir/
+
+# IntelliJ related
+*.iml
+*.ipr
+*.iws
+.idea/
+
+# The .vscode folder contains launch configuration and tasks you configure in
+# VS Code which you may wish to be included in version control, so this line
+# is commented out by default.
+#.vscode/
+
+# Flutter/Dart/Pub related
+**/doc/api/
+**/ios/Flutter/.last_build_id
+.dart_tool/
+.flutter-plugins-dependencies
+.pub-cache/
+.pub/
+/build/
+/coverage/
+
+# Symbolication related
+app.*.symbols
+
+# Obfuscation related
+app.*.map.json
+
+# Android Studio will place build artifacts here
+/android/app/debug
+/android/app/profile
+/android/app/release
+
+# Environment
+.env

examples/demo_spm/.gitignore

@@ -16,6 +16,7 @@ dependencies:
   http: ^1.2.0
   url_launcher: ^6.2.0
   flutter_svg: ^2.0.0
+  flutter_dotenv: ^5.2.1
 
 dev_dependencies:
   flutter_test:
@@ -35,3 +36,4 @@ flutter:
   uses-material-design: true
   assets:
     - assets/onesignal_logo.svg
+    - .env