aggiungi setup Docker per build APK Android

- docker/Dockerfile: ambiente Node 20 + OpenJDK 17 + Android SDK 34
  dist/ ricevuto come volume montato dall'host (non buildata nel container)
- docker/build.sh: esegue npm run build locale poi lancia il container
  flag --head per buildare da HEAD ignorando modifiche non committate
- docker/README.md: requisiti host (x86_64 obbligatorio), utilizzo,
  pipeline e note su prima build (~10-15 min)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/Dockerfile

@@ -0,0 +1,58 @@
+# ── Android SDK + Node (ambiente di build) ────────────────────────────────────
+FROM node:20-slim
+
+# Dipendenze di sistema
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    openjdk-17-jdk-headless \
+    wget \
+    unzip \
+    && rm -rf /var/lib/apt/lists/*
+
+# ── Android SDK ─────────────────────────────────────────────────────────────────
+ENV ANDROID_HOME=/opt/android-sdk
+ENV PATH=$PATH:$ANDROID_HOME/cmdline-tools/latest/bin:$ANDROID_HOME/platform-tools
+
+RUN mkdir -p $ANDROID_HOME/cmdline-tools && \
+    wget -q https://dl.google.com/android/repository/commandlinetools-linux-11076708_latest.zip \
+         -O /tmp/cmdline-tools.zip && \
+    unzip -q /tmp/cmdline-tools.zip -d /tmp && \
+    mv /tmp/cmdline-tools $ANDROID_HOME/cmdline-tools/latest && \
+    rm /tmp/cmdline-tools.zip
+
+RUN yes | sdkmanager --licenses > /dev/null && \
+    sdkmanager \
+        "platform-tools" \
+        "platforms;android-34" \
+        "build-tools;34.0.0"
+
+# ── Progetto (solo dipendenze npm, senza sorgenti) ────────────────────────────
+WORKDIR /app
+
+COPY package*.json ./
+RUN npm ci
+
+# ── Capacitor config ──────────────────────────────────────────────────────────
+RUN cat > capacitor.config.json <<'EOF'
+{
+  "appId": "com.davide.biteplan",
+  "appName": "BitePlan",
+  "webDir": "dist",
+  "server": {
+    "androidScheme": "https"
+  }
+}
+EOF
+
+# ── Installa Capacitor e prepara la piattaforma Android ───────────────────────
+RUN npm install @capacitor/core @capacitor/cli @capacitor/android --save
+
+RUN npx cap add android
+
+# ── Runtime: dist/ viene montato come volume dall'host ────────────────────────
+# build.sh esegue: docker run -v ./dist:/app/dist ...
+# Qui cap sync copia dist/ in android/assets, poi Gradle builda l'APK
+
+CMD npx cap sync android && \
+    cd android && chmod +x gradlew && ./gradlew assembleDebug --no-daemon && \
+    cp app/build/outputs/apk/debug/app-debug.apk /output/biteplan.apk && \
+    echo "APK generato: /output/biteplan.apk"