feat(ostp-client-linux): add CLI VPN client for Linux

New CLI client for Linux with TUN interface support:
- Interactive setup wizard with profile management
- Connect/disconnect commands with root privilege check
- Status monitoring (interface stats, traffic counters)
- Test connection (handshake verification)
- Profile management (add/remove/set-default)
- Anti-VM detection (production mode only)
- Stealth mode (TLS mimicry, geo-SNI selection)

Features:
- Static musl binary (2.0 MB) - universal Linux
- Config storage: ~/.config/ostp/profiles.json
- TUN interface: ostp0 (10.X.Y.Z)
- Security: libc::geteuid() root check, ostp-guard integration
- Error handling: graceful disconnect on Ctrl+C

Commands:
- ostp-client-linux setup             # Interactive wizard
- ostp-client-linux connect --profile default
- ostp-client-linux connect --server 1.2.3.4:443 --psk HEX
- ostp-client-linux status            # Show connection info
- ostp-client-linux disconnect        # Kill running client
- ostp-client-linux profiles list     # List saved profiles
- ostp-client-linux test --server X --psk Y

Distribution updates:
- Added ostp-client-linux (2.0 MB) to linux-x64 package
- Updated SHA256SUMS with all 3 binaries
- Updated README.md with client installation guide
- Rebuilt ostp-server-linux-x64.tar.gz (6.86 MB total)

Note: TUN interface and traffic relay are TODO (placeholders)

Cargo.toml

@@ -1,6 +1,6 @@
 [workspace]
 resolver = "2"
-members = ["ostp", "oncp", "osn", "osds", "ostp-server", "ostp-client", "ostp-guard", "oncp-master", "ostp-daemon", "ostp-installer", "ostp-gui"]
+members = ["ostp", "oncp", "osn", "osds", "ostp-server", "ostp-client", "ostp-client-linux", "ostp-guard", "oncp-master", "ostp-daemon", "ostp-installer", "ostp-gui"]
 
 [workspace.package]
 version = "0.1.0"