feat(portal): replace hardcoded '24/7 内网' stat with live resource count

Backend: bootstrap() now returns stats.total_resources (count of
is_active=True resources).
Frontend: stats adds 'resources' computed from bootstrapStats;
third hero-stat shows '{{ stats.resources }} 资源数量' instead of
the static '24/7 内网' placeholder.

backend/routes/portal.py

@@ -22,6 +22,9 @@ def bootstrap():
     )
     return jsonify({
         "settings": settings,
+        "stats": {
+            "total_resources": Resource.query.filter_by(is_active=True).count(),
+        },
         "categories": [c.to_dict() for c in categories],
         "links": [l.to_dict() for l in links],
     })