Use npx to run next build command

- Replace 'npm run build' with 'npx next build'
- This ensures the next command is found in node_modules/.bin
- Should fix the 'next: not found' error

Dockerfile

@@ -13,8 +13,8 @@ RUN npm ci
 # Copy the rest of the application
 COPY . .
 
-# Build the application
-RUN npm run build
+# Build the application using npx to ensure next is found
+RUN npx next build
 
 # Remove dev dependencies to reduce image size
 RUN npm prune --production