fix(chat): right-align user message row for proper mirror layout

Add align-self: flex-end to .bubbleRowUser so the user message row
sizes to its content and pins to the right edge of the chat area.
Combined with the existing flex-end cross-axis alignment, this places
the user avatar at the right edge with the bubble to its left,
producing a proper left-to-right AI / right-to-left user mirror.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

src/app/chat/components/chat-area.module.css

@@ -46,6 +46,7 @@
   display: flex;
   flex-direction: row;
   align-items: flex-end;
+  align-self: flex-end;
   gap: var(--spacing-1, 4px);
 }