Add Flutter linter for mobile

The older version seemed to be disabled (it was getting triggered on a
non-existent master branch), so I'm not sure if we want this on right now. But
let's give it a go, will remove if it this needs some cleanup first.

.github/workflows/mobile-lint.yml

@@ -0,0 +1,19 @@
+name: "Lint (mobile)"
+
+on:
+    # Run on every push (this also covers pull requests)
+    push:
+        # But only if something changes inside mobile
+        paths:
+            - "mobile/**"
+
+jobs:
+    lint:
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v4
+              with:
+                  submodules: recursive
+            - run: flutter pub get
+            - run: flutter analyze --no-fatal-infos
+            - run: flutter test

mobile/.github/workflows/code_quality.yml

@@ -1,33 +0,0 @@
-name: Check Linter Rules
-on:
-  pull_request:
-    types: [review_requested]
-    branches:
-      - master
-jobs:
-  test:
-    name: Check the source code
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v3
-      - uses: actions/cache@v2
-        with:
-          path: ${{ runner.tool_cache }}/flutter
-          key: flutter-3.0.0-stable
-      # Setup the flutter environment.
-      - uses: subosito/flutter-action@v2.3.0
-        with:
-          channel: 'stable'
-          flutter-version: '3.0.0'
-
-      # Fetch sub modules
-      - run: git submodule update --init --recursive
-
-      # Get flutter dependencies.
-      - name: Install packages
-        run: flutter pub get
-
-      - name: Run Linter
-        run: flutter analyze --no-fatal-infos
-      - name: Run Test
-        run: flutter test