Add CI build and release workflows

Add GitHub Actions workflows mirroring the iOS plugin's CI setup:
- build.yml: runs on PRs to main and manual dispatch, builds with ./gradlew build
- release.yml: manual dispatch with version input, builds, packages addon zip, creates GitHub release

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: DiplomaticRobot

.github/workflows/build.yml

@@ -0,0 +1,32 @@
+name: Build
+
+on:
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - name: Cache Gradle dependencies
+        uses: actions/cache@v5
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle.kts') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: Build plugin
+        run: ./gradlew build

.github/workflows/release.yml

@@ -0,0 +1,52 @@
+name: Release
+run-name: Release ${{ inputs.version }}
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Release version (e.g. 1.0.1)'
+        required: true
+        type: string
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v5
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+
+      - name: Cache Gradle dependencies
+        uses: actions/cache@v5
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle.kts') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      - name: Build plugin
+        run: ./gradlew build
+
+      - name: Package addon zip
+        run: |
+          cd demo
+          zip -r "../GodotFirebaseAndroid-${{ inputs.version }}.zip" addons/GodotFirebaseAndroid
+
+      - name: Create GitHub Release
+        env:
+          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run: |
+          gh release create "${{ inputs.version }}" \
+            --title "GodotFirebaseAndroid ${{ inputs.version }}" \
+            --generate-notes \
+            "GodotFirebaseAndroid-${{ inputs.version }}.zip"