fix(deploy): add spa fallback in frontend image

frontend/Dockerfile

@@ -13,6 +13,23 @@ RUN npm run build
 FROM nginx:alpine
 
 COPY --from=builder /app/dist /usr/share/nginx/html
-# Internal Nginx configuration (Root Nginx acts as reverse proxy to this)
+
+RUN cat <<'EOF' > /etc/nginx/conf.d/default.conf
+server {
+    listen 80;
+    server_name _;
+    root /usr/share/nginx/html;
+    index index.html;
+    location /assets/ {
+        try_files $uri =404;
+        access_log off;
+        expires 30d;
+    }
+    location / {
+        try_files $uri $uri/ /index.html;
+    }
+}
+EOF
+
 EXPOSE 80
 CMD ["nginx", "-g", "daemon off;"]