Refactor data loading: move from inline JSON to client-side fetch

- Remove large JSON data injection from EJS templates
- Add client-side data-loader utility with cache-busting support
- Create server endpoints for JSON data with long-term caching
- Add graceful failure handling if core data fails to load
- Copy JSON data files to dist/data for static hosting
- Update app initialization to load data asynchronously
- Set serverAvailable flag for static builds in gulp task

This reduces HTML payload size and enables better caching strategies
for both server and static deployment modes.

server/scripts/index.mjs

@@ -7,6 +7,7 @@ import { round2 } from './modules/utils/units.mjs';
 import { parseQueryString } from './modules/share.mjs';
 import settings from './modules/settings.mjs';
 import AutoComplete from './modules/autocomplete.mjs';
+import { loadAllData } from './modules/utils/data-loader.mjs';
 
 document.addEventListener('DOMContentLoaded', () => {
 	init();
@@ -28,7 +29,23 @@ const TXT_ADDRESS_SELECTOR = '#txtAddress';
 const TOGGLE_FULL_SCREEN_SELECTOR = '#ToggleFullScreen';
 const BNT_GET_GPS_SELECTOR = '#btnGetGps';
 
-const init = () => {
+const init = async () => {
+	// Load core data first - app cannot function without it
+	try {
+		await loadAllData(typeof OVERRIDES !== 'undefined' && OVERRIDES.VERSION ? OVERRIDES.VERSION : '');
+	} catch (error) {
+		console.error('Failed to load core application data:', error);
+		// Show error message to user and halt initialization
+		document.body.innerHTML = `
+			<div>
+				<h2>Unable to load Weather Data</h2>
+				<p>The application cannot start because core data failed to load.</p>
+				<p>Please check your connection and try refreshing.</p>
+			</div>
+		`;
+		return; // Stop initialization
+	}
+
 	document.querySelector(TXT_ADDRESS_SELECTOR).addEventListener('focus', (e) => {
 		e.target.select();
 	});

server/scripts/modules/utils/data-loader.mjs

@@ -0,0 +1,53 @@
+// Data loader utility for fetching JSON data with cache-busting
+
+let dataCache = {};
+
+// Load data with version-based cache busting
+const loadData = async (dataType, version = '') => {
+	if (dataCache[dataType]) {
+		return dataCache[dataType];
+	}
+
+	try {
+		const url = `/data/${dataType}.json${version ? `?_=${version}` : ''}`;
+		const response = await fetch(url);
+
+		if (!response.ok) {
+			throw new Error(`Failed to load ${dataType}: ${response.status}`);
+		}
+
+		const data = await response.json();
+		dataCache[dataType] = data;
+		return data;
+	} catch (error) {
+		console.error(`Error loading ${dataType}:`, error);
+		throw error;
+	}
+};
+
+// Load all data types
+const loadAllData = async (version = '') => {
+	const [travelCities, regionalCities, stationInfo] = await Promise.all([
+		loadData('travelcities', version),
+		loadData('regionalcities', version),
+		loadData('stations', version),
+	]);
+
+	// Set global variables for backward compatibility
+	window.TravelCities = travelCities;
+	window.RegionalCities = regionalCities;
+	window.StationInfo = stationInfo;
+
+	return { travelCities, regionalCities, stationInfo };
+};
+
+// Clear cache (useful for development)
+const clearDataCache = () => {
+	dataCache = {};
+};
+
+export {
+	loadData,
+	loadAllData,
+	clearDataCache,
+};