feat: aggiungi container Docker dev e build per Flutter

docker/build/: build headless APK Android
- Dockerfile: Ubuntu 22.04 + Java 17 + Flutter stable + Android SDK
- build.sh: genera android/ automaticamente se mancante, poi
  flutter build apk; --release aggiunge zipalign + apksigner

docker/dev/: ambiente di sviluppo web con hot reload
- Dockerfile: Ubuntu 22.04 + Flutter stable (solo web, senza Android SDK)
- docker-compose.yml: espone porta 5173, monta il progetto come volume
- entrypoint.sh: inizializza web/ se mancante, flutter pub get,
  flutter run -d web-server su 0.0.0.0:5173

docker/README.md: documentazione aggiornata per entrambi i container;
rimossi Dockerfile e build.sh Vue/Capacitor non più usati.

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

docker/build/build.sh

@@ -0,0 +1,77 @@
+#!/bin/bash
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "${SCRIPT_DIR}/../.." && pwd)"
+RELEASE=false
+
+for arg in "$@"; do
+  [[ "$arg" == "--release" ]] && RELEASE=true
+done
+
+echo "→ Build immagine biteplan-build..."
+docker build -t biteplan-build "${SCRIPT_DIR}"
+
+if [[ ! -d "${PROJECT_ROOT}/android" ]]; then
+  echo "→ Cartella android/ non trovata, eseguo flutter create..."
+  docker run --rm \
+    -v "${PROJECT_ROOT}:/workspace" \
+    biteplan-build \
+    bash -c "cd /workspace && flutter create --project-name biteplan --org com.biteplan --platforms=android ."
+fi
+
+mkdir -p "${PROJECT_ROOT}/dist"
+
+if [[ "$RELEASE" == "true" ]]; then
+  KEYSTORE="${SCRIPT_DIR}/../biteplan.jks"
+  if [[ ! -f "$KEYSTORE" ]]; then
+    echo "ERRORE: keystore non trovato in docker/biteplan.jks"
+    echo "Generalo con:"
+    echo "  keytool -genkey -v -keystore docker/biteplan.jks -alias biteplan -keyalg RSA -keysize 2048 -validity 10000"
+    exit 1
+  fi
+
+  echo "→ Building release APK..."
+  docker run --rm \
+    -v "${PROJECT_ROOT}:/workspace" \
+    -v "${HOME}/.gradle:/root/.gradle" \
+    biteplan-build \
+    bash -c "cd /workspace && flutter pub get && flutter build apk --release"
+
+  echo "→ Zipalign..."
+  docker run --rm \
+    -v "${PROJECT_ROOT}:/workspace" \
+    biteplan-build \
+    bash -c "zipalign -v -p 4 \
+      /workspace/build/app/outputs/flutter-apk/app-release.apk \
+      /workspace/dist/biteplan-aligned.apk"
+
+  echo "→ Firma APK..."
+  docker run --rm \
+    -v "${PROJECT_ROOT}:/workspace" \
+    -v "$(realpath "${KEYSTORE%/*}"):/keystore:ro" \
+    biteplan-build \
+    bash -c "apksigner sign \
+      --ks /keystore/biteplan.jks \
+      --out /workspace/dist/biteplan-release.apk \
+      /workspace/dist/biteplan-aligned.apk && \
+      rm -f /workspace/dist/biteplan-aligned.apk && \
+      apksigner verify --verbose /workspace/dist/biteplan-release.apk"
+
+  echo ""
+  echo "✓ Release APK: dist/biteplan-release.apk"
+
+else
+  echo "→ Building debug APK..."
+  docker run --rm \
+    -v "${PROJECT_ROOT}:/workspace" \
+    -v "${HOME}/.gradle:/root/.gradle" \
+    biteplan-build \
+    bash -c "cd /workspace && flutter pub get && flutter build apk --debug"
+
+  cp "${PROJECT_ROOT}/build/app/outputs/flutter-apk/app-debug.apk" \
+     "${PROJECT_ROOT}/dist/biteplan-debug.apk"
+
+  echo ""
+  echo "✓ Debug APK: dist/biteplan-debug.apk"
+fi