Add .env configuration for easy environment customization

- Create .env.example with all configurable settings:
  - Server IPs (RU_VDS_IP, DE_VDS_IP)
  - WireGuard ports (WG_CLIENT_PORT, WG_TUNNEL_PORT)
  - VPN networks (USER_VPN_NETWORK, TUNNEL_NETWORK)
  - DNS settings, SSH port, timeouts
- Add .gitignore to exclude .env from version control
- Update setup-ru-vds.sh to read from .env
- Update setup-de-vds.sh to read from .env
- Update add-client.sh to use configuration
- Setup scripts save config to /etc/wireguard/vpn.conf for runtime use
- Update documentation with .env usage instructions

This allows easy deployment to test environments by simply
changing values in .env before running setup scripts.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -123,9 +123,25 @@ vpn.git/
 
 ## Quick Start
 
-1. **Read the implementation plan:** See [IMPLEMENTATION.md](IMPLEMENTATION.md)
-2. **Deploy to servers:** Follow [DEPLOYMENT.md](DEPLOYMENT.md)
-3. **Add clients:** Use scripts in `scripts/` directory
+1. **Configure environment:** Copy `.env.example` to `.env` and adjust values
+2. **Read the implementation plan:** See [IMPLEMENTATION.md](IMPLEMENTATION.md)
+3. **Deploy to servers:** Follow [DEPLOYMENT.md](DEPLOYMENT.md)
+4. **Add clients:** Use scripts in `scripts/` directory
+
+## Configuration
+
+All configurable settings are in `.env` file:
+
+```bash
+cp .env.example .env
+nano .env  # Edit values for your environment
+```
+
+Key settings:
+- `RU_VDS_IP` / `DE_VDS_IP` - Server public IPs
+- `WG_CLIENT_PORT` / `WG_TUNNEL_PORT` - WireGuard ports
+- `USER_VPN_NETWORK` - Client VPN network (default: 10.10.0.0/24)
+- `TUNNEL_*` - Server-to-server tunnel IPs
 
 ## Server File Structure