oops. now need to include postcss.config.js in Dockerfile

frontend/Dockerfile

@@ -9,7 +9,7 @@ COPY package.json pnpm-lock.yaml /app/
 # install dependencies:
 RUN --mount=type=cache,id=pnpm,target=/pnpm/store pnpm install --frozen-lockfile
 # copy what's necessary to build:
-COPY tsconfig.json vite.config.ts index.html index.css tailwind.config.js /app/
+COPY tsconfig.json vite.config.ts index.html index.css postcss.config.js tailwind.config.js /app/
 COPY src /app/src
 # Vite injects envvars at build time, not runtime:
 ENV VITE_SERVER_BASE_URL=https://calendar-optimizer-server.sakal.us