fix: move mention styling outside message (#325)

### 🎯 Goal

Adjust styling of the mention span element so it gets picked up within
message, quoted message and quoted message within message input.

Before:

![image](https://github.com/user-attachments/assets/e67623ab-a660-4ed1-be73-5ecfebdeb6fa)
After:

![image](https://github.com/user-attachments/assets/c955a11e-2309-4847-b3d2-791dbb1cb0bd)

Author: arnautov-anton

src/v2/styles/Message/Message-theme.scss

@@ -191,6 +191,11 @@
   }
 }
 
+.str-chat__message-mention {
+  color: var(--str-chat__message-mention-color);
+  font: var(--str-chat__body2-medium-text);
+}
+
 .str-chat__message {
   @include utils.component-layer-overrides('message');
 
@@ -199,11 +204,6 @@
     color: var(--str-chat__message-link-color);
   }
 
-  .str-chat__message-mention {
-    color: var(--str-chat__message-mention-color);
-    font: var(--str-chat__body2-medium-text);
-  }
-
   .str-chat__message-bubble {
     @include utils.component-layer-overrides('message-bubble');
     font: var(--str-chat__body2-text);