Add Docker improvements and containerization

Dockerfile

@@ -1,25 +1,47 @@
 # ===== STAGE 1: Dependency Installation =====
-FROM node:18 AS deps
+FROM node:20-slim AS deps
 
 WORKDIR /app
 
+# Copy package files and install dependencies
 COPY package*.json ./
 RUN npm ci --omit=dev
 
-COPY . .
-
 # ===== STAGE 2: Runtime =====
-FROM node:18-slim
+FROM node:20-slim
 
+# Install tini for proper signal handling
 RUN apt-get update && apt-get install -y --no-install-recommends \
     tini \
  && rm -rf /var/lib/apt/lists/*
 
+# Create non-root user for better security
+RUN groupadd -r spelling && useradd -r -g spelling spelling
+
+# Setup application directory
 WORKDIR /app
 
-COPY --from=deps /app /app
+# Copy node modules and package files
+COPY --from=deps /app/node_modules /app/node_modules
+COPY --from=deps /app/package*.json /app/
 
+# Copy application code
+COPY . .
+
+# Create and set permissions for data directory
+RUN mkdir -p /app/data && chown -R spelling:spelling /app/data
+
+# Switch to non-root user
+USER spelling
+
+# Set version label
+LABEL version="1.1.0" \
+      description="Spelling Practice Application" \
+      maintainer="nmemmert"
+
+# Expose application port
 EXPOSE 3000
 
+# Use tini as init process and start application
 ENTRYPOINT ["/usr/bin/tini", "--"]
 CMD ["node", "server.js"]