frontend direct testing result and fixes

server.ts

@@ -287,6 +287,18 @@ app.use('/api/reactions', reactionsRouter);
 
 // --- Error Handling and Server Startup ---
 
+// Catch-all 404 handler for unmatched routes.
+// Returns JSON instead of HTML for API consistency.
+app.use((req: Request, res: Response) => {
+  res.status(404).json({
+    success: false,
+    error: {
+      code: 'NOT_FOUND',
+      message: `Cannot ${req.method} ${req.path}`,
+    },
+  });
+});
+
 // Sentry Error Handler (ADR-015) - captures errors and sends to Bugsink.
 // Must come BEFORE the custom error handler but AFTER all routes.
 app.use(sentryMiddleware.errorHandler);