Add serve.json for caching headers and enhance deploy script with asset preservation

public/serve.json

+{
+  "headers": [
+    {
+      "source": "**/*",
+      "headers": [
+        {
+          "key": "Cache-Control",
+          "value": "public, max-age=31536000, immutable"
+        }
+      ]
+    },
+    {
+      "source": "index.html",
+      "headers": [
+        {
+          "key": "Cache-Control",
+          "value": "no-cache, no-store, must-revalidate"
+        }
+      ]
+    },
+    {
+      "source": "service-worker.js",
+      "headers": [
+        {
+          "key": "Cache-Control",
+          "value": "no-cache, no-store, must-revalidate"
+        }
+      ]
+    }
+  ]
+}

scripts/zero-dowtime/deploy.js

 #!/usr/bin/env node
-/* eslint-disable no-shadow */
-/* eslint-disable no-loop-func */
-/* eslint-disable no-await-in-loop */
 
 /**
  * Universal Zero Downtime Deployment Script
@@ -9,17 +6,16 @@
  * All configurations loaded from environment variables
  */
 import { execSync } from 'child_process';
+import { config } from 'dotenv';
 import fs from 'fs';
+import http from 'http';
 import path from 'path';
 import { fileURLToPath } from 'url';
-import http from 'http';
-import { config } from 'dotenv';
 
 // Load environment-specific .env file
 function loadEnvConfig(environment) {
   const envFiles = [`.env.${environment}.local`, `.env.${environment}`, '.env.local', '.env'];
 
-  // eslint-disable-next-line no-restricted-syntax
   for (const envFile of envFiles) {
     const envPath = path.join(process.cwd(), envFile);
     if (fs.existsSync(envPath)) {
@@ -76,9 +72,11 @@ const getConfig = (environment) => ({
 let CONFIG;
 
 // Helper functions
+// eslint-disable-next-line @typescript-eslint/no-shadow
 function logMessage(message, config = CONFIG) {
   const timestamp = new Date().toISOString();
 
+  // eslint-disable-next-line @typescript-eslint/no-shadow
   const logMessage = `[${timestamp}] [${config?.ENVIRONMENT || 'INIT'}] ${message}`;
 
   if (!config || config.ENABLE_CONSOLE_LOG) {
@@ -128,7 +126,6 @@ async function checkHealth(retries = CONFIG.HEALTH_CHECK_RETRIES) {
 
   logMessage(`🏥 Starting health check (${retries} retries)...`);
 
-  // eslint-disable-next-line no-plusplus
   for (let i = 0; i < retries; i++) {
     try {
       await new Promise((resolve, reject) => {
@@ -171,6 +168,31 @@ function atomicFolderSwitch() {
   const finalPath = path.join(process.cwd(), CONFIG.FINAL_DIST_DIR);
   const backupPath = path.join(process.cwd(), CONFIG.BACKUP_DIST_DIR);
 
+  // Preserve old assets to prevent 404s during transition
+  logMessage('📦 Preserving old assets to prevent 404s...');
+  const oldAssetsDir = path.join(finalPath, 'assets');
+  const newAssetsDir = path.join(tmpPath, 'assets');
+
+  if (fs.existsSync(oldAssetsDir) && fs.existsSync(newAssetsDir)) {
+    try {
+      const files = fs.readdirSync(oldAssetsDir);
+      let copiedCount = 0;
+
+      for (const file of files) {
+        const srcFile = path.join(oldAssetsDir, file);
+        const destFile = path.join(newAssetsDir, file);
+
+        if (!fs.existsSync(destFile)) {
+          fs.copyFileSync(srcFile, destFile);
+          copiedCount += 1;
+        }
+      }
+      logMessage(`✅ Preserved ${copiedCount} old asset files.`);
+    } catch (error) {
+      logMessage(`⚠️ Failed to preserve assets: ${error.message}`);
+    }
+  }
+
   // Create backup of current dist
   if (fs.existsSync(finalPath)) {
     if (fs.existsSync(backupPath)) {
@@ -444,5 +466,4 @@ if (process.argv[1] === fileURLToPath(import.meta.url)) {
   deployApp(environment);
 }
 
-// eslint-disable-next-line import/prefer-default-export
 export { deployApp };