Fix serving issue: remove index.txt and add explicit root route

- Remove .txt files from build output that caused download prompts
- Add explicit location = / rule to ensure index.html is served

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -8,5 +8,6 @@ RUN npm run build
 FROM nginx:alpine
 COPY nginx.conf /etc/nginx/conf.d/default.conf
 COPY --from=builder /app/out /usr/share/nginx/html
+RUN rm -f /usr/share/nginx/html/*.txt
 EXPOSE 80
 CMD ["nginx", "-g", "daemon off;"]

nginx.conf

@@ -17,7 +17,11 @@ server {
     add_header X-XSS-Protection "1; mode=block" always;
     add_header Referrer-Policy "strict-origin-when-cross-origin" always;
 
-    # Handle Next.js static export routes
+    # Serve index.html for root and all routes (SPA fallback)
+    location = / {
+        try_files /index.html =404;
+    }
+
     location / {
         try_files $uri $uri.html $uri/index.html /index.html;
     }