fix: nginx serves index.html with no-cache headers

Vite hashes all JS/CSS assets, so those can be cached for 30 days.
But index.html must never be cached — it references the current hashes.
Caching index.html meant users ran old JS after deploys.

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

Dockerfile

@@ -19,6 +19,10 @@ RUN echo 'server { \
     listen 3000; \
     root /usr/share/nginx/html; \
     index index.html; \
+    location = /index.html { \
+    expires -1; \
+    add_header Cache-Control "no-store, no-cache, must-revalidate"; \
+    } \
     location / { \
     try_files $uri $uri/ /index.html; \
     expires 30d; \
@@ -44,4 +48,4 @@ RUN chown -R nginx:nginx /usr/share/nginx/html \
     && chown -R nginx:nginx /var/log/nginx
 
 # Expose HTTP port (NPM will handle HTTPS)
-EXPOSE 3000
+EXPOSE 3000