Replace GitHub Actions with Gitea workflow

.gitea/workflows/android.yml

@@ -0,0 +1,28 @@
+name: Android CI
+
+on:
+  push:
+    branches:
+      - master
+      - main
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: "17"
+
+      - name: Set up Android SDK
+        uses: android-actions/setup-android@v3
+
+      - name: Build debug APK
+        working-directory: android
+        run: ./gradlew assembleDebug --no-daemon