fix: persist SQLite database via host bind mount

Mount ./data:/app/data in both compose files and set DATABASE_URL to
the absolute path /app/data/velxio.db so the database survives container
restarts and updates. Create /app/data in Dockerfile.standalone.

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

Dockerfile.standalone

@@ -55,6 +55,9 @@ RUN arduino-cli config init \
 
 WORKDIR /app
 
+# Data directory for persistent SQLite database (mounted as a volume at runtime)
+RUN mkdir -p /app/data
+
 # Install Python backend dependencies
 COPY backend/requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt

docker-compose.prod.yml

@@ -7,6 +7,10 @@ services:
     restart: unless-stopped
     ports:
       - "3080:80"
+    environment:
+      - DATABASE_URL=sqlite+aiosqlite:////app/data/velxio.db
+    volumes:
+      - ./data:/app/data
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost/health"]
       interval: 30s

docker-compose.yml

@@ -6,6 +6,10 @@ services:
     ports:
       - "8001:8001"
     restart: unless-stopped
+    environment:
+      - DATABASE_URL=sqlite+aiosqlite:////app/data/velxio.db
+    volumes:
+      - ./data:/app/data
     healthcheck:
       test: ["CMD", "python", "-c", "import urllib.request; urllib.request.urlopen('http://localhost:8001/health')"]
       interval: 30s