ci(android): add Forgejo Actions workflows for debug APK builds

Adds .forgejo/workflows/ with two workflows that run on the self-hosted
vega-runner (Forgejo act_runner with Nix support):

- build-fdroid-debug.yml: builds fdroidDebug variant (no Firebase)
- build-play-debug.yml: builds playDebug variant (with Firebase)

Both install the Android SDK via command-line tools, set up JDK 21,
cache Gradle, build the APK, and upload artifacts.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

.forgejo/workflows/build-fdroid-debug.yml

@@ -0,0 +1,62 @@
+name: Build F-Droid Debug APK
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'app/**'
+      - '.forgejo/workflows/build-fdroid-debug.yml'
+  pull_request:
+    branches: [main]
+    paths:
+      - 'app/**'
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Install Android SDK
+        run: |
+          set -e
+          export ANDROID_HOME=$HOME/android-sdk
+          export ANDROID_SDK_ROOT=$ANDROID_HOME
+          mkdir -p $ANDROID_HOME/cmdline-tools
+          curl -sSL https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip -o /tmp/cmdline-tools.zip
+          unzip -q /tmp/cmdline-tools.zip -d $ANDROID_HOME/cmdline-tools
+          mv $ANDROID_HOME/cmdline-tools/cmdline-tools $ANDROID_HOME/cmdline-tools/latest
+          export PATH="$ANDROID_HOME/cmdline-tools/latest/bin:$PATH"
+          yes | sdkmanager --licenses >/dev/null 2>&1 || true
+          sdkmanager "platform-tools" "platforms;android-36" "build-tools;36.0.0"
+          echo "ANDROID_HOME=$ANDROID_HOME" >> $GITHUB_ENV
+          echo "ANDROID_SDK_ROOT=$ANDROID_HOME" >> $GITHUB_ENV
+          echo "$ANDROID_HOME/platform-tools" >> $GITHUB_PATH
+
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+
+      - name: Cache Gradle
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.gradle/caches
+            ~/.gradle/wrapper
+          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
+          restore-keys: ${{ runner.os }}-gradle-
+
+      - name: Build F-Droid Debug APK
+        run: ./gradlew :app:assembleFdroidDebug --no-daemon --stacktrace
+
+      - name: Upload APK
+        uses: actions/upload-artifact@v4
+        with:
+          name: centralcloud-oncall-fdroid-debug-${{ github.run_id }}
+          path: app/build/outputs/apk/fdroid/debug/*.apk

.forgejo/workflows/build-play-debug.yml

@@ -0,0 +1,62 @@
+name: Build Play Debug APK
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'app/**'
+      - '.forgejo/workflows/build-play-debug.yml'
+  pull_request:
+    branches: [main]
+    paths:
+      - 'app/**'
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Install Android SDK
+        run: |
+          set -e
+          export ANDROID_HOME=$HOME/android-sdk
+          export ANDROID_SDK_ROOT=$ANDROID_HOME
+          mkdir -p $ANDROID_HOME/cmdline-tools
+          curl -sSL https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip -o /tmp/cmdline-tools.zip
+          unzip -q /tmp/cmdline-tools.zip -d $ANDROID_HOME/cmdline-tools
+          mv $ANDROID_HOME/cmdline-tools/cmdline-tools $ANDROID_HOME/cmdline-tools/latest
+          export PATH="$ANDROID_HOME/cmdline-tools/latest/bin:$PATH"
+          yes | sdkmanager --licenses >/dev/null 2>&1 || true
+          sdkmanager "platform-tools" "platforms;android-36" "build-tools;36.0.0"
+          echo "ANDROID_HOME=$ANDROID_HOME" >> $GITHUB_ENV
+          echo "ANDROID_SDK_ROOT=$ANDROID_HOME" >> $GITHUB_ENV
+          echo "$ANDROID_HOME/platform-tools" >> $GITHUB_PATH
+
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: '21'
+          distribution: 'temurin'
+
+      - 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-
+
+      - name: Build Play Debug APK
+        run: ./gradlew :app:assemblePlayDebug --no-daemon --stacktrace
+
+      - name: Upload APK
+        uses: actions/upload-artifact@v4
+        with:
+          name: centralcloud-oncall-play-debug
+          path: app/build/outputs/apk/play/debug/*.apk