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/build.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
+OUTPUT_DIR="$PROJECT_ROOT/output"
+DIST_DIR="$PROJECT_ROOT/dist"
+
+FROM_HEAD=false
+for arg in "$@"; do
+  [[ "$arg" == "--head" ]] && FROM_HEAD=true
+done
+
+echo "==> Preparazione cartelle..."
+mkdir -p "$OUTPUT_DIR"
+
+# ── Build Vite ────────────────────────────────────────────────────────────────
+if $FROM_HEAD; then
+  COMMIT_SHA=$(git -C "$PROJECT_ROOT" rev-parse --short HEAD)
+  echo "==> Build Vite da HEAD ($COMMIT_SHA)..."
+  TMPDIR=$(mktemp -d)
+  trap 'rm -rf "$TMPDIR"' EXIT
+  git -C "$PROJECT_ROOT" archive HEAD | tar -x -C "$TMPDIR"
+  cd "$TMPDIR"
+  npm ci --silent
+  npm run build --silent
+  DIST_DIR="$TMPDIR/dist"
+  cd "$PROJECT_ROOT"
+else
+  echo "==> Build Vite dalla working directory..."
+  cd "$PROJECT_ROOT"
+  npm run build --silent
+fi
+
+# ── Build immagine Docker ─────────────────────────────────────────────────────
+echo "==> Build immagine Docker..."
+docker build \
+    -f "$SCRIPT_DIR/Dockerfile" \
+    -t biteplan-builder \
+    "$PROJECT_ROOT"
+
+# ── Generazione APK (dist/ montato come volume) ───────────────────────────────
+echo "==> Generazione APK..."
+docker run --rm \
+    -v "$DIST_DIR:/app/dist:ro" \
+    -v "$OUTPUT_DIR:/output" \
+    biteplan-builder
+
+echo ""
+echo "APK pronto in: $OUTPUT_DIR/biteplan.apk"