fix: resolve stuck detecting state for panel stats on subpath deploy

Always inject panel_base from PANEL_PATH for static/API URLs and set
SCRIPT_NAME in middleware so /api/stats works behind nginx subpaths.

Co-authored-by: Cursor <cursoragent@cursor.com>

panel/templates/dashboard.html

@@ -107,5 +107,5 @@
 </div>
 {% endblock %}
 {% block scripts %}
-<script src="{{ url_for('static', filename='app.js') }}"></script>
+<script src="{{ panel_base }}/static/app.js"></script>
 {% endblock %}