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.

CAPROVER-DEPLOYMENT-FIX.md

@@ -0,0 +1,74 @@
+# CapRover Deployment Fix for 500 Errors
+
+## 🚨 Issue
+The domain privacy changes require specific environment variables to be set in CapRover. Missing these causes 500 errors during deployment.
+
+## ✅ Required Environment Variables in CapRover
+
+### **Step 1: Set Environment Variables**
+In your CapRover app settings, add these environment variables:
+
+```bash
+# Required for API routing
+API_BASE_URL=https://your-backend-domain.com
+API_HOSTNAME=your-backend-domain.com
+SERVER_API_URL=https://your-backend-domain.com/api
+
+# Client-side API URL (should already be set)
+NEXT_PUBLIC_API_URL=/api
+```
+
+### **Step 2: Example Configuration**
+Replace `your-backend-domain.com` with your actual backend domain:
+
+```bash
+# For production deployment
+API_BASE_URL=https://internal-api.inboxi.ng
+API_HOSTNAME=internal-api.inboxi.ng
+SERVER_API_URL=https://internal-api.inboxi.ng/api
+NEXT_PUBLIC_API_URL=/api
+```
+
+### **Step 3: Alternative - Use Internal Service Names**
+If using CapRover's internal networking:
+
+```bash
+# Using CapRover internal service names
+API_BASE_URL=http://srv-captain--your-backend-app-name
+API_HOSTNAME=srv-captain--your-backend-app-name
+SERVER_API_URL=http://srv-captain--your-backend-app-name/api
+NEXT_PUBLIC_API_URL=/api
+```
+
+## 🔧 Troubleshooting
+
+### **Check Environment Variables**
+In CapRover app logs, you should see:
+```
+Building with environment:
+- API_BASE_URL: https://your-domain.com
+- API_HOSTNAME: your-domain.com
+- SERVER_API_URL: https://your-domain.com/api
+```
+
+### **Common Issues**
+1. **Undefined variables**: Set all required variables in CapRover
+2. **Invalid URLs**: Ensure no trailing slashes in API_BASE_URL
+3. **HTTPS vs HTTP**: Match your backend's protocol
+
+### **Verification**
+After deployment, check:
+1. App starts without 500 errors
+2. API requests work correctly
+3. No console warnings about undefined variables
+
+## 🚀 Deploy Steps
+1. Set environment variables in CapRover
+2. Commit and push changes
+3. Redeploy the app
+4. Check logs for successful startup
+
+## 📝 Notes
+- The `next.config.mjs` now has safer fallbacks to prevent 500 errors
+- Missing variables will log warnings but won't crash the app
+- For local development, use the `.env` file as before