fix: use true red for important instructions

- Add $ui-red to colors.css (hsla(0, 100%, 50%, 1))
- Use $ui-red for .important-instruction in connection-modal.css

Co-Authored-By: Gemini <noreply@google.com>

Author: takaokouji

src/components/connection-modal/connection-modal.css

@@ -449,5 +449,5 @@
 
 .important-instruction {
     font-weight: bold;
-    color: $red-primary;
+    color: $ui-red;
 }

src/css/colors.css

@@ -15,6 +15,8 @@ $ui-black-transparent-10: hsla(0, 0%, 0%, 0.10); /* 10% transparent version of b
 $ui-green: hsla(163, 85%, 35%, 1); /* #0DA57A */
 $ui-green-2: hsla(163, 85%, 40%, 1); /* #0FBD8C */
 
+$ui-red: hsla(0, 100%, 50%, 1); /* #FF0000 */
+
 $text-primary: hsla(225, 15%, 40%, 1); /* #575E75 */
 $text-primary-transparent: hsla(225, 15%, 40%, 0.75);