fix critical issues in ROI calculator

- Replace hardcoded Django template tags in JavaScript with runtime CSRF token retrieval
- Add comprehensive error handling for Chart.js dependencies and missing DOM elements
- Enhance input validation with safe fallbacks for malformed number parsing
- Add graceful degradation when external libraries fail to load

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

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

hub/services/templates/calculator/csp_roi_calculator.html

@@ -3,6 +3,10 @@
 
 {% block title %}CSP ROI Calculator{% endblock %}
 
+{% block extra_head %}
+<meta name="csrf-token" content="{{ csrf_token }}">
+{% endblock %}
+
 {% block extra_css %}
 <link rel="stylesheet" type="text/css" href='{% static "css/roi-calculator.css" %}'>
 {% endblock %}