Add pre-deployment IP configuration guide for network transitions

- Add HOST_IP field to .env.example with documentation
- Improve TRUSTED_PROXIES comments with examples
- Create PRE_DEPLOYMENT_IP_CONFIGURATION.md guide
- Update deployment docs with network transition workflow
- Add comprehensive IP configuration checklist

.env.example

@@ -21,7 +21,10 @@ ADMIN_EMAIL=admin@your-domain.com
 # DATABASE_URL=
 
 # Server Configuration
+# Set BEFORE deployment if host will have static IP after restart
+# This IP/domain will be used for SSL certificates and nginx configuration
 DOMAIN=your-domain.com
+HOST_IP=192.168.0.121
 EMAIL=admin@your-domain.com
 PREFERRED_URL_SCHEME=https
 
@@ -50,4 +53,10 @@ SESSION_COOKIE_HTTPONLY=true
 SESSION_COOKIE_SAMESITE=Lax
 
 # Proxy Configuration (configured in app.py)
-TRUSTED_PROXIES=10.0.0.0/8,172.16.0.0/12,192.168.0.0/16
+# IMPORTANT: Set this to your actual network range or specific proxy IP
+# Examples:
+#   - 192.168.0.0/24 (local network with /24 subnet)
+#   - 10.0.0.0/8 (AWS or similar cloud)
+#   - 172.16.0.0/12 (Docker networks)
+# For multiple IPs: 192.168.0.121,10.0.1.50
+TRUSTED_PROXIES=192.168.0.0/24