Create Firebase Test Lab GitHub Actions workflow

This commit introduces a new GitHub Actions workflow to run Android UI tests on Firebase Test Lab.

- The workflow is triggered on pushes and pull requests to the `main` branch.
- It builds the debug app and test APKs.
- It authenticates with Google Cloud and runs instrumentation tests on a Pixel 6 device.
- A link to the Firebase Test Lab results is provided in the workflow output.

Author: JoshLudahl

.github/workflows/firebase-test-lab.yml

@@ -0,0 +1,70 @@
+name: Android UI Tests (Firebase Test Lab)
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  firebase-test-lab:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+
+    steps:
+      # 1. Checkout code
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      # 2. Set up JDK (adjust version if needed)
+      - name: Set up JDK
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+
+      # 3. Cache Gradle (important for speed)
+      - name: Cache Gradle
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+          restore-keys: |
+            ${{ runner.os }}-gradle-
+
+      # 4. Build APKs (app + androidTest)
+      - name: Build app and test APKs
+        run: |
+          ./gradlew assembleDebug assembleDebugAndroidTest
+
+      # 5. Authenticate to Google Cloud
+      - name: Authenticate to Google Cloud
+        uses: google-github-actions/auth@v2
+        with:
+          credentials_json: ${{ secrets.GCP_SA_KEY }}
+
+      # 6. Set up gcloud CLI
+      - name: Set up gcloud
+        uses: google-github-actions/setup-gcloud@v2
+        with:
+          project_id: ${{ secrets.GCP_PROJECT_ID }}
+
+      # 7. Run Firebase Test Lab instrumentation tests
+      - name: Run tests on Firebase Test Lab
+        run: |
+          gcloud firebase test android run \
+            --type instrumentation \
+            --app app/build/outputs/apk/debug/app-debug.apk \
+            --test app/build/outputs/apk/androidTest/debug/app-debug-androidTest.apk \
+            --device model=Pixel6,version=33,locale=en,orientation=portrait \
+            --timeout 15m \
+            --results-bucket=${{ secrets.GCP_PROJECT_ID }}-test-lab-results
+
+      # 8. (Optional) Always print link to results
+      - name: Firebase Test Lab results info
+        if: always()
+        run: |
+          echo "View test results in the Firebase Console:"
+          echo "https://console.firebase.google.com/project/${{ secrets.GCP_PROJECT_ID }}/testlab"