refactor: clean up health check and task access logic by removing unused code

backend/app/routes/health.py

@@ -1,10 +1,13 @@
 """Health check endpoint."""
 from flask import Blueprint, jsonify
 
+from app.extensions import limiter
+
 health_bp = Blueprint("health", __name__)
 
 
 @health_bp.route("/health", methods=["GET"])
+@limiter.exempt
 def health_check():
     """Simple health check — returns 200 if the service is running."""
     return jsonify({