perf: switch to node:20-alpine base images

Dockerfile

@@ -2,9 +2,9 @@
 # Builds the MCP server with SQLite persistence
 
 # Stage 1: Build backend (TypeScript compilation + native modules)
-FROM node:20-slim AS builder
+FROM node:20-alpine AS builder
 
-RUN apt-get update && apt-get install -y python3 make g++ && rm -rf /var/lib/apt/lists/*
+RUN apk add --no-cache python3 make g++
 
 WORKDIR /app
 
@@ -16,12 +16,12 @@ COPY tsconfig.json ./
 RUN npm run build:server
 
 # Stage 2: Production MCP Server
-FROM node:20-slim AS production
+FROM node:20-alpine AS production
 
-RUN apt-get update && apt-get install -y python3 make g++ && rm -rf /var/lib/apt/lists/*
+RUN apk add --no-cache python3 make g++
 
-RUN addgroup --system --gid 1001 nodejs && \
-    adduser --system --uid 1001 --gid 1001 nodejs
+RUN addgroup -S -g 1001 nodejs && \
+    adduser -S -u 1001 -G nodejs nodejs
 
 WORKDIR /app
 
@@ -29,7 +29,7 @@ COPY package*.json ./
 RUN --mount=type=cache,target=/root/.npm npm ci --omit=dev
 
 # Remove build tools after native modules are compiled
-RUN apt-get purge -y python3 make g++ && apt-get autoremove -y
+RUN apk del python3 make g++
 
 COPY --from=builder /app/dist ./dist