Items 10-15: ES modules, inline style cleanup, template modal, code modernization

- Item 10: Convert to ES modules with import/export, single module entry point
- Item 11: Replace inline styles with CSS classes (background overlay, card
  animations, highlight effect, config modal form elements)
- Item 12: Move ConfigManager modal HTML from JS template literal to
  <template> element in index.html
- Item 13: Replace deprecated url.parse() with new URL() in server.js
  and update route handlers to use searchParams
- Item 14: Replace JSON.parse/stringify deep clone with structuredClone()
- Item 15: Remove dead JSON-fixing regex code from departures.js route

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

public/js/utils/logger.js

@@ -95,6 +95,9 @@ class Logger {
 // Create a singleton instance
 const logger = new Logger();
 
-// Export both the class and the singleton instance
+// ES module export
+export { Logger, logger };
+
+// Keep window reference for backward compatibility
 window.Logger = Logger;
 window.logger = logger;