Add unit tests for ProfileRepository and implement new shaders

- Created `NativeAssetsManifest.json` and added font and shader assets for unit tests.
- Implemented `ink_sparkle.frag` and `stretch_effect.frag` shaders for visual effects.
- Developed unit tests for `ProfileRepository` to validate API interactions for fetching and updating user profiles.
- Utilized Mockito for mocking API client responses in tests.

flutter/Dockerfile

@@ -11,6 +11,9 @@ COPY . .
 # Generate localizations (ARB -> Dart) before the main build.
 RUN flutter gen-l10n
 
+# Run tests
+RUN flutter test
+
 # Inject API base URL at build time via --dart-define.
 # Default to same-origin /api to avoid mixed-content in HTTPS deployments.
 ARG API_BASE_URL=/api