Fix SSE route dependency and align architecture docs

frontend/src/components/ui/Button.tsx

@@ -1,5 +1,5 @@
 import React from 'react';
-import { useTheme } from '../../contexts/ThemeContext';
+import { useTheme } from '../../contexts';
 
 interface ButtonProps {
   variant?: 'primary' | 'secondary';
@@ -57,4 +57,4 @@ export const Button: React.FC<ButtonProps> = ({
       {children}
     </button>
   );
-};
+};