Use FVM in GitHub Actions and migrate to Flutter 3.32.4 (#641)

* feat: implement Flutter version management using FVM across CI workflows

* Flutter 3.29.3 + minor Package upgrades

* Replace deprecated `withOpacity`

* Upgrade major package versions without breaking changes.

* Disable unnecessary_async rule

Re-enable later

* New language version and automated fixes

- unnecessary_breaks
- unnecessary_underscore

* Update BUILDING.md to use fvm commands

* Add gitignore files for Android and iOS build artifacts

* Migrate iOS dependencies to Swift Package Manager

This is being done automatically by Flutter

* Flutter 3.32.4

* New sdk version

* docs: add IDE setup instructions and troubleshooting guide for FVM integration

.github/workflows/ios.yaml

@@ -17,20 +17,33 @@ jobs:
       uses: actions/checkout@v3
       with:
         submodules: recursive
+
     - name: Setup Java
       uses: actions/setup-java@v3
       with:
         distribution: 'temurin'
         java-version: '11'
+
+    - name: Setup FVM
+      id: fvm-config-action
+      uses: kuhnroyal/flutter-fvm-config-action@v2
+
     - name: Setup Flutter
       uses: subosito/flutter-action@v2
       with:
-        flutter-version: '3.32.2'
-        channel: 'stable'
+        flutter-version: ${{ steps.fvm-config-action.outputs.FLUTTER_VERSION }}
+        channel: ${{ steps.fvm-config-action.outputs.FLUTTER_CHANNEL }}
+        cache: true
+        cache-key: "flutter-:os:-:channel:-:version:-:arch:-:hash:"
+        cache-path: "${{ runner.tool_cache }}/flutter/:channel:-:version:-:arch:"
+        pub-cache-key: "flutter-pub:os:-:channel:-:version:-:arch:-:hash:"
+        pub-cache-path: "${{ runner.tool_cache }}/flutter/:channel:-:version:-:arch:"
+
     - name: Collect Translation Files
       run: |
         cd lib/l10n
         python3 collect_translations.py
+
     - name: Build for iOS
       run: |
         flutter pub get