Add mobile Flutter CI workflow (#488)

* Add mobile Flutter CI workflow

* Fix Flutter message sorting with null timestamps

.github/workflows/README.md

@@ -7,6 +7,7 @@
 - **`python.yml`** - Python ingestor pipeline
 - **`ruby.yml`** - Ruby Sinatra app testing
 - **`javascript.yml`** - Frontend test suite
+- **`mobile.yml`** - Flutter mobile tests with coverage reporting
 
 ## Usage
 

.github/workflows/mobile.yml

@@ -0,0 +1,52 @@
+# Copyright © 2025-26 l5yth & contributors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: Mobile
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  flutter:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./app
+    steps:
+    - uses: actions/checkout@v5
+    - name: Set up Flutter
+      uses: subosito/flutter-action@v2
+      with:
+        channel: stable
+        cache: true
+    - name: Install dependencies
+      run: flutter pub get
+    - name: Run Flutter tests with coverage
+      run: flutter test --coverage
+    - name: Upload coverage to Codecov
+      if: always()
+      uses: codecov/codecov-action@v5
+      with:
+        token: ${{ secrets.CODECOV_TOKEN }}
+        files: coverage/lcov.info
+        flags: flutter-mobile
+        name: flutter-mobile
+      env:
+        CODECOV_TOKEN: ${{ secrets.CODECOV_TOKEN }}