nav resilience after pool restart, thinner marker rings, drop dead marker popup

shopdb/__init__.py

@@ -244,11 +244,23 @@ def register_frontend_routes(app: Flask):
         # (the probe was a path-traversal risk surface).
         if path:
             try:
-                return send_from_directory(frontend_dist, path)
+                response = send_from_directory(frontend_dist, path)
+                # Asset filenames carry a content hash, so a given URL never
+                # changes - cache them hard. Everything else stays revalidated.
+                if path.startswith('assets/'):
+                    response.headers['Cache-Control'] = 'public, max-age=31536000, immutable'
+                else:
+                    response.headers['Cache-Control'] = 'no-cache'
+                return response
             except Exception:
                 pass
 
-        return send_from_directory(frontend_dist, 'index.html')
+        # index.html names the hashed chunks, so a stale copy points at files a
+        # deploy has already deleted and the SPA stops navigating. Always
+        # revalidate it.
+        response = send_from_directory(frontend_dist, 'index.html')
+        response.headers['Cache-Control'] = 'no-cache'
+        return response
 
 
 def configure_logging(app: Flask):