fix: tailwind v4 postcss, auth-server session, eslint cleanups

frontend/Dockerfile

@@ -1,7 +1,7 @@
 # syntax=docker/dockerfile:1.6
 
 ############ Base ############
-FROM node:24-alpine AS base
+FROM node:20-alpine AS base
 WORKDIR /app
 RUN apk add --no-cache bash curl tzdata \
  && ln -snf /usr/share/zoneinfo/Asia/Bangkok /etc/localtime \
@@ -66,6 +66,8 @@ RUN echo "=== Checking components ===" && \
     echo "=== Checking .next permissions ===" && \
     ls -lad /app/.next
     
+RUN npm ci --no-audit --no-fund --include=dev
+
 RUN npm run build
 
 ############ Prod runtime (optimized) ############