chore: add nexusguard.conf.example for native install, gitignore conf file

.gitignore

@@ -13,6 +13,7 @@ Desktop.ini
 .env
 .env.local
 .env.production
+nexusguard.conf
 
 # Logs
 *.log

nexusguard.conf.example

@@ -0,0 +1,35 @@
+# ==========================================
+# NexusGuard SD-WAN - Configuration
+# ==========================================
+# For native (non-Docker) installations.
+# Install to /etc/nexusguard/nexusguard.conf
+# Env vars always take precedence over this file.
+
+# 1. Database Configuration (PostgreSQL)
+DB_HOST=127.0.0.1
+DB_PORT=5432
+DB_USER=nexusguard
+DB_PASSWORD=nexusguard
+DB_NAME=nexusguard
+
+# 2. Redis Configuration
+REDIS_ADDR=127.0.0.1:6379
+
+# 3. Security & Cryptography
+# Generate using: openssl rand -hex 32
+JWT_SECRET=changeme
+SERVER_SALT=changeme
+
+# 4. Networking & SD-WAN
+NFTABLES_TABLE=nexusguard
+IPAM_POOL=10.8.0.0/16
+
+# 5. General Settings
+GIN_MODE=release
+LOG_LEVEL=info
+
+# 6. CORS Configuration
+CORS_ALLOWED_ORIGINS=http://localhost:5173
+
+# 7. Share Link Configuration
+SHARE_LINK_TTL=24h