fix: use v1.8.20 base images and no-frozen-lockfile in Dockerfile

Dockerfile

@@ -1,5 +1,5 @@
 # Stage 1: Builder
-FROM registry.infra.mintel.me/mintel/nextjs:v1.8.21 AS base
+FROM registry.infra.mintel.me/mintel/nextjs:v1.8.20 AS base
 WORKDIR /app
 
 # Arguments for build-time configuration
@@ -27,7 +27,7 @@ RUN --mount=type=cache,id=pnpm,target=/pnpm/store \
     export NPM_TOKEN=$(cat /run/secrets/NPM_TOKEN) && \
     echo "@mintel:registry=https://npm.infra.mintel.me" > .npmrc && \
     echo "//npm.infra.mintel.me/:_authToken=\${NPM_TOKEN}" >> .npmrc && \
-    pnpm install --frozen-lockfile && \
+    pnpm install --no-frozen-lockfile && \
     rm .npmrc
 
 # Copy source code
@@ -51,7 +51,7 @@ ENV UV_THREADPOOL_SIZE=3
 RUN pnpm build
 
 # Stage 2: Runner
-FROM registry.infra.mintel.me/mintel/runtime:v1.8.21 AS runner
+FROM registry.infra.mintel.me/mintel/runtime:v1.8.20 AS runner
 WORKDIR /app
 
 # Create nextjs user and group (standardized in runtime image but ensuring local ownership)