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)

ostp-client-linux/Cargo.toml

@@ -0,0 +1,29 @@
+[package]
+name = "ostp-client-linux"
+version.workspace = true
+edition.workspace = true
+description = "OSTP Stealth VPN Client for Linux"
+
+[[bin]]
+name = "ostp-client-linux"
+path = "src/main.rs"
+
+[dependencies]
+ostp = { path = "../ostp" }
+ostp-guard = { path = "../ostp-guard" }
+osn = { path = "../osn" }
+tokio.workspace = true
+anyhow.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+clap.workspace = true
+hex.workspace = true
+serde.workspace = true
+serde_json.workspace = true
+dialoguer.workspace = true
+console.workspace = true
+libc = "0.2"
+nix = { version = "0.29", features = ["net", "ioctl"] }
+
+[target.'cfg(target_os = "linux")'.dependencies]
+# Linux-specific TUN interface