Add CapRover deployment fix and improve env var handling

Added CAPROVER-DEPLOYMENT-FIX.md with instructions for required environment variables to prevent 500 errors. Improved validation and fallback logic for SERVER_API_URL and API_BASE_URL in server-api.ts, route.ts, and next.config.mjs to handle missing or invalid values gracefully and log warnings instead of crashing.

next.config.mjs

@@ -24,10 +24,23 @@ const baseConfig = {
     ],
   },
   async rewrites() {
+    const apiBaseUrl = process.env.API_BASE_URL || 'http://localhost:3001';
+    
+    // Ensure API_BASE_URL is valid to prevent 500 errors
+    if (!apiBaseUrl || apiBaseUrl === 'undefined') {
+      console.warn('API_BASE_URL not set, using localhost fallback');
+      return [
+        {
+          source: '/api/:path*',
+          destination: 'http://localhost:3001/api/:path*',
+        },
+      ];
+    }
+    
     return [
       {
         source: '/api/:path*',
-        destination: `${process.env.API_BASE_URL || 'http://localhost:3001'}/api/:path*`,
+        destination: `${apiBaseUrl}/api/:path*`,
       },
     ];
   },