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/dev/Dockerfile

@@ -0,0 +1,16 @@
+FROM ubuntu:22.04
+
+ENV DEBIAN_FRONTEND=noninteractive \
+    FLUTTER_HOME=/opt/flutter \
+    PATH="/opt/flutter/bin:${PATH}"
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl git unzip xz-utils ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN git clone --depth 1 --branch stable \
+        https://github.com/flutter/flutter.git /opt/flutter && \
+    flutter config --no-analytics --enable-web && \
+    flutter precache --web
+
+WORKDIR /workspace

docker/dev/docker-compose.yml

@@ -0,0 +1,14 @@
+services:
+  dev:
+    build: .
+    ports:
+      - "5173:5173"
+    volumes:
+      - ../../:/workspace
+      - pub-cache:/root/.pub-cache
+    command: bash /workspace/docker/dev/entrypoint.sh
+    stdin_open: true
+    tty: true
+
+volumes:
+  pub-cache:

docker/dev/entrypoint.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+set -e
+
+# Aggiunge supporto web se mancante (crea solo web/, non tocca lib/)
+if [[ ! -d /workspace/web ]]; then
+  echo "→ Inizializzazione supporto web..."
+  flutter create . --platforms=web
+fi
+
+flutter pub get
+exec flutter run -d web-server --web-hostname=0.0.0.0 --web-port=5173