Revert "Dockerfile: make this work for clean builds also."

This reverts commit d0386ee8ac.

Dockerfile

@@ -8,8 +8,8 @@ COPY package*.json ./
 COPY frontend/package*.json ./frontend/
 
 # Install dependencies
-RUN npm i
-RUN cd frontend && npm i
+RUN npm ci
+RUN cd frontend && npm ci
 
 # Copy source files
 COPY . .
@@ -26,7 +26,7 @@ WORKDIR /app
 
 # Install only production dependencies
 COPY package*.json ./
-RUN npm i --production
+RUN npm ci --production
 
 # Copy built files
 COPY --from=builder /app/build ./build