This commit implements several JavaScript optimizations across the web templates:

Performance Improvements:
- Replace unbind().click() pattern with event delegation in admin/templates.html
  to eliminate repeated event handler attachment/detachment on DataTables draw
- Optimize string concatenation in loops using array.join() in admin/manage.html
- Add DOM element caching to reduce repeated jQuery queries
- Optimize DataTables rendering in overview.html by caching cells array
  and using for loops instead of .each()
- Add responsive chart resizing for ECharts in scoreboard.html

Code Quality & Maintainability:
- Create shared utils.js library for common validation functions
- Extract and deduplicate validator code from service.html and admin/service.html
- Replace inline validation functions with reusable utilities

Security Enhancements:
- Add sanitization for dynamic ID generation in admin/status.html
  to prevent potential XSS vulnerabilities
- Implement proper AJAX error handling in scoreboard.html and admin/templates.html

Bug Fixes:
- Fix typo in flags.html (extra 'i' character on line 89)

All changes maintain backward compatibility while improving performance,
maintainability, and security of the JavaScript codebase.