Make tag text bold for better readability

Add font-weight: 600 to tag labels to improve text readability
on solid colored backgrounds. The bold text provides better
contrast and matches the visual weight of the desktop app.

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

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

templates/tasks/_task_item.html

@@ -28,7 +28,7 @@
             <span class="task-meta-separator">·</span>
             {% endif %}
             {% for tag in task.tags.all %}
-            <span class="task-group-label" style="background-color: {{ tag.color }}; color: white;">
+            <span class="task-group-label" style="background-color: {{ tag.color }}; color: white; font-weight: 600;">
                 {{ tag.name }}
             </span>
             {% endfor %}