cleanup: remove ~70 lines of duplicate CSS for conversation view styles

First block of conversation-view, conversations-list, conversation-message,
message-header, sender, timestamp, message-content, message-attachments was
silently overridden by identical selectors defined later. Kept the unique
reaction/delete-button styles.

bot/static/index.html

@@ -242,69 +242,6 @@
     }
 
     /* Conversation View Styles */
-    .conversation-view {
-      max-width: 800px;
-      margin: 0 auto;
-    }
-    
-    .conversations-list {
-      max-height: 600px;
-      overflow-y: auto;
-      border: 1px solid #444;
-      border-radius: 8px;
-      padding: 1rem;
-      background: #222;
-    }
-    
-    .conversation-message {
-      margin-bottom: 1rem;
-      padding: 0.75rem;
-      border-radius: 8px;
-      border-left: 4px solid;
-    }
-    
-    .conversation-message.user-message {
-      background: #2a2a3a;
-      border-left-color: #4CAF50;
-    }
-    
-    .conversation-message.bot-message {
-      background: #3a2a2a;
-      border-left-color: #2196F3;
-    }
-    
-    .message-header {
-      display: flex;
-      justify-content: space-between;
-      align-items: center;
-      margin-bottom: 0.5rem;
-      font-size: 0.9rem;
-    }
-    
-    .sender {
-      font-weight: bold;
-      color: #fff;
-    }
-    
-    .timestamp {
-      color: #999;
-      font-size: 0.8rem;
-    }
-    
-    .message-content {
-      color: #ddd;
-      white-space: pre-wrap;
-      word-wrap: break-word;
-    }
-    
-    .message-attachments {
-      margin-top: 0.5rem;
-      padding: 0.5rem;
-      background: rgba(255,255,255,0.05);
-      border-radius: 4px;
-      font-size: 0.9rem;
-    }
-    
     .message-reactions {
       margin-top: 0.5rem;
       display: flex;