refactor: switch to alpine base image

Dockerfile

@@ -1,47 +1,31 @@
 # Build frontend in a dedicated stage
-FROM node:24-slim AS frontend-build
+FROM node:24-alpine AS frontend-build
 WORKDIR /app/frontend
 COPY frontend/package*.json frontend/package-lock*.json ./
 RUN npm ci --silent
 COPY frontend/ .
 RUN npm run build
 
-# Final image: build backend, generate Prisma client, prune dev deps, and include frontend dist
-FROM node:24-slim AS final
+# Final runtime image
+FROM node:24-alpine
 WORKDIR /app
-
-# install minimal OS deps
-RUN apt-get update -y \
-&& apt-get install -y openssl
-
 # copy package manifests and install deps (leverage Docker cache)
 COPY backend/package*.json backend/package-lock*.json ./backend/
 RUN cd backend && npm ci --silent
-
 # copy backend source (schema, migrations, source)
 COPY backend ./backend
-
 # generate Prisma client against a harmless temp DB path (does not apply migrations)
 RUN cd backend && DATABASE_URL="file:./data/sqlite.db" npx prisma generate --schema=./prisma/schema.prisma || true
-
 # remove devDependencies to slim image
 RUN cd backend && npm prune --production --silent
-
 # install prisma CLI into final image so entrypoint can run migrate deploy at runtime
 RUN cd backend && npm i --no-audit --no-fund prisma --silent || true
-
-# copy entrypoint (added below) and make executable
+# copy entrypoint and make executable
 COPY docker/entrypoint.sh /usr/local/bin/entrypoint.sh
 RUN chmod +x /usr/local/bin/entrypoint.sh
-
 # Copy built frontend into the expected location: /app/frontend/dist
 COPY --from=frontend-build /app/frontend/dist ./frontend/dist
 
-# runtime environment (DATA_DIR used at runtime; DATABASE_URL points to it)
-ENV NODE_ENV=production
-ENV DATA_DIR=/data
-ENV DATABASE_URL="file:${DATA_DIR}/sqlite.db"
-
 WORKDIR /app/backend
 EXPOSE 3000