fix(admin): use npm workspace in Docker

Align admin production and development images with the repository's committed npm workspace and lockfile. This ensures shared and Expo-linked dependencies are installed before the admin build runs.

apps/admin/Dockerfile

@@ -2,19 +2,12 @@ FROM node:20-bookworm-slim AS builder
 
 WORKDIR /app
 
-# Enable pnpm via corepack (allow non-matching packageManager)
-ENV COREPACK_ENABLE_STRICT=0
-ENV PNPM_CONFIG_LINK_WORKSPACE_PACKAGES=true
-RUN corepack enable && corepack prepare pnpm@9.15.0 --activate
-
-# Copy everything first (workspaces need full structure)
+# Copy the npm workspace and install from its committed lockfile.
 COPY . .
-
-# Install all dependencies
-RUN pnpm install --no-frozen-lockfile
+RUN npm ci
 
 # Build shared package first
-RUN pnpm exec turbo run build --filter=@sauci/shared
+RUN npm run build -w @sauci/shared
 
 # Build admin app with env vars
 ARG VITE_SUPABASE_URL
@@ -41,7 +34,7 @@ ENV VITE_COUNCIL_ENABLED=$VITE_COUNCIL_ENABLED
 ENV VITE_COUNCIL_GENERATOR_MODEL=$VITE_COUNCIL_GENERATOR_MODEL
 ENV VITE_COUNCIL_REVIEWER_MODEL=$VITE_COUNCIL_REVIEWER_MODEL
 
-RUN pnpm exec turbo run build --filter=@sauci/admin
+RUN npm run build -w @sauci/admin
 
 FROM nginx:alpine
 COPY --from=builder /app/apps/admin/dist /usr/share/nginx/html