refactor: Hide guillemets and add line break after quote

- Guillemets (» «) no longer displayed - styling is sufficient
- Added line break after quoted text for better readability
- Raw message still contains guillemets for compatibility

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/static/js/message-utils.js

@@ -53,7 +53,8 @@ function processQuotes(text) {
     const quotePattern = /»([^«]+)«/g;
 
     return text.replace(quotePattern, (_match, quoted) => {
-        return `<span class="quote-text">»${quoted}«</span>`;
+        // Display without guillemets (styling is enough) + line break after
+        return `<span class="quote-text">${quoted}</span><br>`;
     });
 }