feat: add Docker build

Dockerfile

@@ -0,0 +1,41 @@
+# Build stage
+FROM node:20-alpine AS builder
+
+WORKDIR /app
+
+# Copy package files
+COPY package*.json ./
+
+# Install dependencies
+RUN npm ci --only=production
+
+# Runtime stage
+FROM node:20-alpine
+
+# Install wget for health checks
+RUN apk --no-cache add wget
+
+WORKDIR /app
+
+# Copy dependencies from builder
+COPY --from=builder /app/node_modules ./node_modules
+
+# Copy application files
+COPY package*.json ./
+COPY server ./server
+COPY presets ./presets
+COPY public ./public
+
+# Create non-root user (let Alpine assign available GID/UID)
+RUN addgroup spore && \
+    adduser -D -s /bin/sh -G spore spore && \
+    chown -R spore:spore /app
+
+USER spore
+
+# Expose port
+EXPOSE 8080
+
+# Run the application
+CMD ["node", "server/index.js"]
+