add gradle build workflow

.gitea/workflows/gradle-build.yml

@@ -0,0 +1,47 @@
+name: Build
+
+on:
+  push:
+
+jobs:
+  Gradle-Build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@v4
+
+    - name: Set up JDK
+      uses: actions/setup-java@v4
+      with:
+        java-version: '23'
+        check-latest: true
+        distribution: 'zulu'
+
+    - name: Setup Gradle
+      uses: gradle/actions/setup-gradle@v4
+      with:
+        add-job-summary: always
+        cache-cleanup: on-success
+
+    - name: Cache Gradle dependencies
+      uses: actions/cache@v4
+      with:
+        path: | 
+          ~/.gradle/caches
+        key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+        restore-keys: |
+          ${{ runner.os }}-gradle-
+
+    - name: Build
+      run: chmod +x gradlew; ./gradlew assemble
+
+    - name: Move artifacts
+      run: mkdir artifacts; mv app/build/libs/*.jar artifacts;
+
+    - name: Upload artifact
+      uses: christopherhx/gitea-upload-artifact@v4
+      with:
+        name: artifacts
+        path: artifacts