refactor(backend): update environment variable handling and replace VITE_IS_PLATFORM with IS_PLATFORM constant

server/load-env.js

@@ -0,0 +1,24 @@
+// Load environment variables from .env before other imports execute.
+import fs from 'fs';
+import path from 'path';
+import { fileURLToPath } from 'url';
+import { dirname } from 'path';
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+try {
+  const envPath = path.join(__dirname, '../.env');
+  const envFile = fs.readFileSync(envPath, 'utf8');
+  envFile.split('\n').forEach(line => {
+    const trimmedLine = line.trim();
+    if (trimmedLine && !trimmedLine.startsWith('#')) {
+      const [key, ...valueParts] = trimmedLine.split('=');
+      if (key && valueParts.length > 0 && !process.env[key]) {
+        process.env[key] = valueParts.join('=').trim();
+      }
+    }
+  });
+} catch (e) {
+  console.log('No .env file found or error reading it:', e.message);
+}