feat: custom wireguard port - #366

Init machine with custom wireguard port:
```
uc machine add [email protected] -c default --wg-port 51823 -n host
```
Add machine with custom wireguard port:
```
uc machine add [email protected] -c default --wg-port 51823 -n host
```
Custom Wireguard port:
```
❯ ./uncloud machine ls
NAME       STATE   ADDRESS         PUBLIC IP      WIREGUARD ENDPOINTS                      MACHINE ID
host       Up      10.210.2.1/24   xx.xx.xxx.3    xx.xx.xxx.3:51823                        ffb6f370c69553fbf90c4e8541531944
```

- Rename `network.WireGuardPort` to `network.DefaultWireGuardPort` for clarity
- Rename `network.Config.ListenPort` field to `network.Config.WireGuardPort` for consistency
- Rename `network.Config.EffectiveListenPort()` method to `network.Config.EffectiveWireGuardPort()`
- Update all references across CLI commands (add, init, update), internal machine logic, and experiments
- Improves naming consistency and makes the purpose of the port configuration more explicit

…or endpoints

- Add port range validation (1-65535) in machine add and init commands
- Update ParseWireGuardEndpoints to accept configurable default port parameter
- Pass custom --wg-port value as default when parsing endpoints instead of hardcoded constant
- Update help text to reference --wg-port value instead of hardcoded port number
- Remove unnecessary network package import from flags.go
- Regenerate protobuf files with updated protoc versions (v1.34.2 and v5.27.3)
- Ensures WireGuard endpoints use the configured port when port is omitted from endpoint specification