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>

server.js

@@ -2,7 +2,6 @@
 require('dotenv').config();
 
 const http = require('http');
-const url = require('url');
 const fs = require('fs');
 const path = require('path');
 
@@ -52,7 +51,7 @@ loadSitesConfig();
 
 // Create HTTP server
 const server = http.createServer(async (req, res) => {
-  const parsedUrl = url.parse(req.url, true);
+  const parsedUrl = new URL(req.url, `http://${req.headers.host || 'localhost'}`);
   
   res.setHeader('Access-Control-Allow-Origin', '*');
   res.setHeader('Access-Control-Allow-Methods', 'GET, POST, OPTIONS');
@@ -72,7 +71,7 @@ const server = http.createServer(async (req, res) => {
     sitesRouter.handleSiteSearch(req, res, parsedUrl);
   }
   else if (parsedUrl.pathname === '/api/sites/nearby') {
-    sitesRouter.handleNearbySites(req, res, parsedUrl);
+    await sitesRouter.handleNearbySites(req, res, parsedUrl);
   }
   else if (parsedUrl.pathname === '/api/config') {
     configRouter.handleGetConfig(req, res, config);