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.

lib/server-api.ts

@@ -22,6 +22,17 @@ try {
  */
 function getServerApiUrl(endpoint: string): string {
   const apiUrl = process.env.SERVER_API_URL || 'http://localhost:3001/api';
+  
+  // Validate API URL to prevent 500 errors
+  if (!apiUrl || apiUrl === 'undefined' || apiUrl === 'null') {
+    console.warn('SERVER_API_URL not properly set, using localhost fallback');
+    const fallbackUrl = 'http://localhost:3001/api';
+    const cleanEndpoint = endpoint.startsWith('/') ? endpoint.substring(1) : endpoint;
+    return fallbackUrl.endsWith('/') 
+      ? `${fallbackUrl}${cleanEndpoint}`
+      : `${fallbackUrl}/${cleanEndpoint}`;
+  }
+  
   const cleanEndpoint = endpoint.startsWith('/') ? endpoint.substring(1) : endpoint;
   
   return apiUrl.endsWith('/')