Replace setup-env action with reusable flutter-setup workflow; streamline CI configuration and enhance dependency management

.github/actions/setup-env.yaml

@@ -1,25 +0,0 @@
-name: 🛠️ Setup Env
-
-on:
-  workflow_call:
-    inputs:
-      flutter_version:
-        required: false
-        type: string
-        default: "stable"
-        description: "Flutter version to use. Default is 'stable'."
-jobs:
-  setup:
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-        with:
-          submodules: recursive
-      - name: Set up Flutter
-        uses: subosito/flutter-action@v2
-        with:
-          channel: "${{ inputs.flutter_version }}"
-          flutter-version-file: pubspec.yaml
-      - name: Install dependencies
-        run: flutter pub get